chapter one - Who You Belong To || Ryomen Sukuna
ryomen sukuna x f!reader
❝When a brilliant but emotionally guarded psychiatrist takes on Ryomen Sukuna—a volatile, obsessive man with a violent past—as her court-mandated patient, neither anticipates the dangerous intimacy that will unfold. What begins as a clinical relationship spirals into an all-consuming entanglement of lust, trust, and possession. As the lines blur between doctor and lover, savior and sinner, she must confront the scars of her own past while navigating the overwhelming devotion of a man who’s never known softness—until her. Love was never part of the treatment plan. But now, she might be the only cure he's ever wanted.❞
cw ; mdni • 18+ only. contains explicit sexual themes and content. use of alcohol. hurt/trauma. smut . anxiety. death. graphic scenes. murder. tw. psychological.
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The case file lay open on your desk, the soft glow of your brass reading lamp catching on the sharp black print of his name—
Itadori, Sukuna R. Age: 30. Released from Fuchū Prison exactly six days ago. Charged with double homicide.
Diagnosis: Antisocial Personality Disorder, Obsessive-Compulsive tendencies, and persistent impulsivity. Documented history of violent behavior dating back to adolescence. Two psychiatric holds during incarceration due to physical altercations with guards and fellow inmates. No medications prescribed. No history of therapy engagement.
You sat back slowly, fingertips brushing your lower lip in silent thought. His case was transferred to your clinic at the discretion of the parole board, marked urgent. Court-mandated weekly evaluations. Unmedicated. Unrepentant. A high-risk patient. The kind you rarely got unless they were shackled to a chair and sedated. You adjusted your blouse with a small sigh, pushing your curls away from your eyes and rising to straighten the lines of your skirt. You were tired—emotionally more than physically. It had been a long week, and your final appointment was now a known murderer with crimson eyes and a superiority complex, if the warden's handwritten note at the bottom of the file was to be believed—
"Thinks he’s smarter than everyone. May be. Do not underestimate him."
The knock on your door was firm. One strike. Not hesitant. Not rushed. You opened it yourself—something you always did. A small gesture of trust, neutrality. You had read once in school that first impressions were just as important for clinicians as for patients. He stepped inside like he already owned the room. Tall—immense, actually. Built like something carved from lean stone. Buzzed pink hair, tattoos curling up the side of his neck. A fitted black button-down, sleeves rolled up to the elbows. He looked like he’d walked out of a fashion spread for a dangerous man, not ten years of incarceration. You motioned to the seat across from your chair. “Sukuna Itadori?”
“Depends who’s asking,” he said, low and indifferent, as his crimson eyes dragged over the room—and then over you. Not in the lecherous way you’d come to expect from certain inmates fresh out of long-term lockup. No. His gaze was worse. Measured. Amused. Hungry for something he hadn’t yet named. You ignored the chill threading your spine. “I’m Dr. L/N. I’ll be handling your psychiatric evaluations from here forward.” He took the seat. Legs spread. One arm slung over the back of the chair. His eyes didn’t leave you once. “You read my file, I assume,” he said casually. “What’d it say about me?” You didn’t answer the question.
Instead, you folded your hands over your lap. “This is a mandated session. I want to make it clear that my role is not law enforcement. I am not here to interrogate you. I am here to evaluate your mental state, understand your risk level, and monitor your behavioral health as you transition back into society.” He tilted his head. “So you’re here to judge me.”
“I’m here to observe you.” A smirk tugged at his mouth. Sharp canines. “Same thing.” It wasn’t the first time you’d encountered patients like him. High-risk. Violent. Intelligent. But there was something about the way he looked at you—as if this wasn’t a legal requirement but rather… an opportunity. “You’ve had other therapists?” you asked, keeping your tone neutral. “Nope,” he replied. “I don’t talk to people I don’t trust.”
“Then let’s start simple. How are you sleeping?”
“I sleep like the dead,” he replied coolly. “Figured that’d amuse you.” You didn’t flinch. “Any nightmares?” He smiled. “Would you like me to have nightmares, doc?”
“I’d like you to answer the question.” He stared for a long moment. Silent. Calculating. “No. No nightmares.” You made a note in your file. “Still journaling compulsively?” you asked, that got his attention. His eyes narrowed, the smirk fading into something colder. “So you did read the file.”
“I read every file.” He leaned forward then, elbows on his knees, voice low. “Then you know I killed them both. And you know why.”
You didn’t respond. Not yet.
Because this was a test.
Every word, every flicker of his crimson gaze, every silence—a test. He wanted to see how far he could push you. How much of your professionalism was real. How much fear you could swallow before it showed. “I know the facts,” you said, carefully. “I don’t know you.” Sukuna leaned back. That amused smirk returned, faint but there. “That’s what you’re hoping to change, huh?” No. Not hope. Mandate. But you didn’t say that. Instead, you crossed your legs and kept your voice steady, professional, distant. “Tell me about your week. What’s it been like adjusting to life outside?” He stretched, slow and loose like a cat sizing up a bird. “Quiet,” he said simply. “Too quiet. People don’t make eye contact anymore. But you do. You must not know better.”
“I’ve read your file,” you said softly. “I know exactly what you are, Mr. Itadori.” He smiled wider. “Then you’ll be the first.” You wrote that down.
Observation: Inflated sense of uniqueness. Acute self-awareness. Confidence bordering on delusional. Fixation on clinician’s eye contact.
You could feel it already—the thread of his attention beginning to tighten. Like a hook just under the skin. Nothing violent yet. Just a pull and from the way he was still watching you—unblinking, chin propped against his knuckles, silent—you understood one thing very clearly.
He didn’t see you as his doctor.
Not yet. Maybe not ever.
You saw the shift in his posture when you stood. The way his eyes flicked to your waist, then back up, deliberately. He didn’t mask his focus. He didn’t have to. “Same time next week,” you said, reaching for the door. “Sure,” he drawled. “I’ll be thinking about you ‘til then.” You didn’t answer. Didn’t turn. You just opened the door and walked him out and still—you felt his eyes on you the entire time.
You stared at the open laptop screen, cursor blinking beside the words “Initial Observation Summary: Itadori, Sukuna R.” Your fingers hovered above the keys, unmoving. A subtle ache had begun to form just behind your left eye, the kind of headache that came not from light or strain, but pressure—from trying to contain something that wasn’t meant to be contained. You rolled your shoulders back, exhaled once, and finally began to type:
Subject: Itadori, Sukuna R. (30, Male) Session 1 of 12 (Mandated weekly psychiatric evaluation) The patient arrived on time. No physical aggression. No immediate signs of psychotic breaks or dissociative behavior. Physical presentation: confident posture, deliberate eye contact, hyper-awareness of spatial control. Psychological profile as observed today aligns with previous reports—namely: manipulative tendencies, lack of remorse, and high verbal intelligence. Narcissistic undertones. The patient exhibited no interest in therapeutic engagement. However, demonstrated deep interest in me as the clinician—evidenced by continuous eye contact, fixation on my movements, multiple attempts at control through subtle conversational pivots and provocative remarks. Note: Patient observed the room with the attention of someone assessing for weakness rather than comfort. There were no mentions of regret, remorse, or even curiosity regarding the crimes committed. He mentioned the murders immediately—unsolicited—and spoke of them as though testing my reaction. Recommendation: Maintain professional boundary at all costs. Observe for obsessive patterns. Avoid unnecessary personal disclosure. Subject is to be considered highly observant, emotionally detached, and prone to fixation.
Your fingers paused. You blinked. That last line didn’t feel clinical. It felt personal. Too personal. You sighed and leaned back in your chair, rubbing your thumb along your temple as the silence of your office grew heavier. It wasn’t fear that settled in your chest. You were no stranger to danger—threats were a part of your profession, particularly with high-risk patients. No, what you felt… was something more subtle. More suffocating.
Watched— even now. As if the crimson of his eyes had bled into the air, and something in the room remembered them—burned into the walls like an afterimage. You closed the file and shut your laptop— enough for tonight.
“Hey, you made it,” Shoko said, raising her glass lazily from across the booth. She wore her white coat open over a black turtleneck, cigarette tucked behind her ear even though the bar didn’t allow smoking indoors. “I was beginning to think the new patient already killed you.” You slid into the booth without reacting, lifting your own drink—whiskey neat—and letting the warmth settle into your throat like armor. “I’m more worried he wants to marry me,” you muttered dryly. Utahime, who had been scrolling through her phone with one perfectly arched brow raised, perked up. “Wait, wait. The Sukuna Itadori? Double homicide guy?” Shoko’s grin curled around the rim of her drink. “She had her first session with him today. Apparently he’s charming, sucks it was your day off Utah.”
“He’s not charming,” you said automatically. “He’s…” You trailed off, because you didn’t have the right word yet. Not even close— Shoko tilted her head. “He’s what?” You took a slow sip of your drink. The ice had melted slightly, softening the bite. You didn’t answer right away.
“He’s… dangerous in a way that doesn’t advertise itself. It’s all… under the surface. Controlled. Clean.” Utahime blinked. “Okay, that’s more terrifying than if he just yelled at you.”
“Exactly,” you murmured. You leaned back against the worn leather of the booth and stared at the condensation sliding down your glass. Your hair stuck slightly to the back of your neck. The room was warm, but you couldn’t shake the subtle cold pressing beneath your skin. “He asked if I wanted him to have nightmares,” you said, mostly to yourself, Utahime gave a small scoff. “Jesus.”
“He smiled when he said it. Not sadistically. Not cruel. Just... like it was interesting to him. Like I was interesting.” That was the part that unnerved you. Because it wasn’t the threat of violence that lingered—it was the precision of it. Sukuna Itadori wasn’t a beast behind bars. He wasn’t a man led by impulse. That would’ve been easier. He was calculated. And now he was free. “Do you want to drop the case?” Shoko asked, voice softer now, though not without bite. “Because you can. No one would blame you.” You looked at her, slow and still. “I don’t want to,” you said quietly. The admission surprised even you. It slipped out too easily.
Utahime raised a brow. “You don’t?” You shook your head. “I want to understand him.” You didn’t say it out loud, but what you really meant was this— I need to know what he’s seeing when he looks at me, because whatever it is—it’s already looking back.
The takeout container sat open on the chipped countertop, still steaming. Greasy yakitori skewers, rice packed tight, a side of pickled cabbage he wouldn’t touch. One bare bulb swung overhead, the chain rattling softly whenever a gust of wind rattled through the old frame. Sukuna cracked open a can of beer with one hand, leaned his weight against the counter, and stared at the black screen of the muted TV across the room. He was still getting used to the silence, not the kind that hovered between conversations. No, true silence—the kind that came when steel doors weren’t slamming shut, when voices weren’t echoing down cinderblock halls, when no one was watching your every movement like prey on a leash. It wasn’t freedom that felt strange.
It was emptiness.
He exhaled through his nose, slow, and dragged the back of his hand over the scarred side of his jaw, smearing grease and sweat along the curve of his cheekbone. Construction work was rough, long hours, and his shoulders ached from hauling rebar all day. But Toji hadn’t asked many questions—just clapped him on the back with a grin, tossed him a vest, and said “Don’t kill anybody. I need this contract.” The beer was cold. Sharp. Cheap— He liked it that way. He tore off another bite of chicken with his teeth and chewed lazily, one hip cocked against the counter, his other hand resting on the waist of his sweats. The tattoos along his fingers caught in the low light, bold and unapologetic, a roadmap of ink that no parole board could erase and then—you.
Like a fucking film reel stitched into the inside of his skull. You, sitting behind your desk, all smooth edges and soft quiet. You, with that voice of silk-covered authority, trying to pretend your pulse didn’t shift the moment he leaned forward. You, in that pale blouse, the line of your bra just barely visible when you crossed your arms. Green eyes sharp but too gentle, like you hadn’t yet learned the world didn’t care about kindness.
You’d looked at him.
Really looked.
Not like a threat. Not like a pity case.
But like a puzzle. And he liked puzzles.
He scoffed, a low sound in his chest, and shook his head—but the smirk curled against his lip before he could stop it. “‘I know what you are,’” he muttered to himself, mocking your tone, beer can balanced lazily in one hand. “Sweetheart, you haven’t got a fucking clue.” His cock was already swelling—just from the thought. He let the can thud against the counter as he dragged his hand beneath the waistband of his sweats, fingers wrapping around himself with a hissed breath. No preamble. No hesitation. Just that sudden, hot ache of blood rushing downward and the soft burn of want curling in his gut.
You did that.
Not the barista down the block. Not the woman across the hall who left perfume trails in the hallway.
You.
Professional. Poised. Reserved. He wondered if you’d still sound that calm with your thighs spread open for him, if you’d keep your clinical voice when he shoved his cock so deep you’d forget your own name. He could already hear you gasping—soft, broken sounds, hands grabbing at his forearms because you wouldn’t be able to take all of him at once. You wouldn’t even know what to do with a man like him and fuck, he wanted to teach you. He stroked himself slow at first, long firm pulls, letting the pressure build behind his eyes as his hips flexed forward, chasing the friction. A moan slid from his throat—sharp, involuntary—and he threw his head back, picturing your mouth slack, lips wet from kissing, green eyes fluttering shut while he whispered filth into your ear.
“Bet you’d be so tight for me,” he muttered, jaw clenching, teeth bared now. “So damn soft.” You wouldn’t cry. No, not you. But you’d shake. You’d tremble and you’d come undone for him once he broke you open. The smirk twisted into something darker—more possessive. You were smart, but not as smart as you thought. Strong, but not invulnerable and soon—soon you’d realize that no one understood you like he would.
Not your colleagues. Not your friends. Not any of the other sad little patients who walked through your door.
Only him.
Only Sukuna.
He came with a low, guttural curse, jaw tight, stomach flexing as release spilled hot across his knuckles. His chest rose and fell hard. Muscles taut. Neck damp with sweat. The beer was still cold. The chicken still untouched, but the room felt warmer now. Quieter. He wiped his hand on a paper towel without looking, already reaching for another can.
Because this wasn’t over.
Not even close.
He'd see you again next week.
And he couldn’t fucking wait.
You noticed the rain before you noticed him— the soft roll of thunder in the distance. The faint patter of water tapping against the glass. It was a dull rhythm—soft, unthreatening—but steady and somehow, it made everything inside your office feel smaller.
More intimate.
You were sitting at your desk again, same place, same posture—but not the same ease. Not with him arriving in less than five minutes. You’d reviewed your notes from last week twice already. Every word. Every silence. Every look. You’d even called Shoko after hours the night of your first session just to talk through your instincts—not because you needed permission to trust them, but because saying them aloud might sharpen the shape of what you were dealing with. There was something coiled beneath Sukuna Itadori’s surface. Not just violence. Not even just pathology.
Something targeted— and it had begun curling itself around you.
The door opened without a knock this time.
Your hand instinctively flexed around the pen you held—your only reaction. He stepped inside wearing the same unbuttoned black shirt from last week, sleeves still rolled to the elbow, tattoos peeking beneath the edge of his collar. His buzzed pink hair looked freshly done, clean edges. There was rain on his shoulders, beading down the leather jacket he wore loosely over his broad frame. “Doc,” he greeted, like this was a regular occurrence. Like you were meeting for coffee. “Mr. Itadori,” you answered calmly, nodding toward the chair. “Have a seat.”
“Already so cold,” he murmured as he sat, spreading his knees again, arms resting relaxed—but ready—on the armrests. “Miss me?” You didn’t answer. Instead, you tapped the corner of your notepad. “Let’s begin where we left off.” His grin widened, but he didn’t push. You observed him quietly for a moment. His pupils weren’t dilated. Breathing steady. He had a relaxed posture, but there was an alertness behind the façade—like a lion pretending to nap beside prey. “Any physical altercations this week?” you asked, he snorted. “What, you think I decked my boss at the job site?”
“You have a documented history of violence toward figures of authority. I’m asking a clinical question.” He leaned back, drumming his fingers lazily on the armrest. “No fights. Though a guy whistled at a woman walking past and I nearly put a hammer through his knee. Does fantasizing count?” You paused. “Did you act on that impulse?”
“I smiled at him,” Sukuna said, his grin feral. “That was enough. He didn’t say anything else the rest of the day.” You jotted it down—
reliance on intimidation as conflict resolution. Reluctance to regulate impulses. No follow-through, but volatile instincts remain present.
“How are you adjusting to post-incarceration routine?” you asked next, he rolled his neck like the question bored him. “Work is easy. Toji keeps the crew in line. I wake up, lift heavy shit, go home. Watch TV. Eat. Try not to get hard thinking about you.” You didn’t blink. “Sukuna,” you said, finally using his first name. Slowly. “If you're not going to take this seriously—”
“Oh, I’m taking it very seriously,” he interrupted, voice dropping low. “I’ve been thinking about this session all week.”
“Thinking about me is not the same as engaging in treatment.”
“It’s why I’m here, isn’t it?” You narrowed your eyes slightly. “Why are you here, Sukuna?” He stilled, you could see the shift behind his eyes—like a shadow moving behind glass. “No jokes,” you said quietly. “No deflections. No flirtation. Just answer the question. Do you actually want to do this? Or is this just another box you plan to check off until your parole ends?” He didn’t speak for a moment.
The silence was full of tension, but not the explosive kind.
It was decisive. Intentful.
Then, his voice came low and even.
“I’ve been told what I am my entire life. Broken. Cold. Sick. I spent ten years in a cage with worse monsters than me, and I walked out just as sane as I walked in.” He leaned forward, elbows on his knees now, that unreadable expression returning. “So yeah. I’m curious. About how someone like you plans to figure me out.” You didn’t look away. “I don’t plan to figure you out.”
“No?”
“I plan to understand you. There’s a difference.” A beat and then—for the first time—he looked genuinely interested. Not amused. Not predatory.
Interested. “What’s the difference?”
“Figuring someone out is control. It’s ego. It’s ownership. Understanding someone is slower. Mutual. It requires trust.” He tilted his head. “Big word for someone I just told I jerked off thinking about.”
“You’re not the first patient to sexualize me as a form of distraction,” you said, voice crisp, clinical. “But you’re certainly the most performative about it.” That made him laugh. A sharp, loud bark that echoed in the room. He shook his head, dragging a hand down his face, eyes gleaming.
“You’re good, doc,” he said, low. “Fucking hell.”
“I’m not trying to be good. I’m trying to help you.”
“Then ask me what you really want to ask.” You paused, eyes narrowing slightly and then you did. “Why did you kill them?” His smile died instantly.
Gone. The air shifted—charged now. Not explosive. But volatile. Like something had been touched inside him that wasn’t meant to be disturbed.
He stared at you and for a moment, the quiet stretched long between you, just the storm outside starting to rattle the windows.
“Do you want the truth?” he asked softly. “I want whatever version you’re willing to give.” He leaned forward, forearms braced on his thighs, voice dropping to a near whisper. “My father never loved anyone but himself. My ex-wife was too much like him. She thought betrayal was clever. Thought playing people was a kind of art. And they thought I’d never see it. That I’d be too proud. Too slow. Too fucking blind.” You watched the shift in his jaw—the way his throat worked, the flare of his nostrils. “I didn’t kill them because I was angry,” he said. “I killed them because they thought I wouldn’t.” That silence again. Thick. Wet. Drenched in truth too heavy to lift.
You wrote nothing. Said nothing.
Because he’d given you something and he knew it.
You met his eyes again. “Thank you for answering.” He smiled—but this one was different. Quieter. Darker. “You’ll think about that later tonight,” he said. “I bet you’ll try not to.”
“I think about a lot of my patients,” you said evenly. “It’s part of the job.”
“But I’m not like your other patients,” he said, sitting back now. “Am I?” You didn’t respond. Because he already knew the answer. The timer on your desk buzzed softly. Session over, but neither of you moved. He rose slowly, straightened his jacket, adjusted the cuffs like a man preparing for something more important than a walk back to the parking lot. You stood too, maintaining eye contact. You needed to. Because turning your back on someone like Sukuna wasn’t just foolish—it was dangerous.
“I’ll see you next week,” you said calmly, he reached the door.
Paused.
Then looked back over his shoulder, gaze burning crimson in the low light. “You’re the first person I’ve told the real reason,” he said. “Don’t make me regret it.” And then he left—silent as shadow.
The scratching of pen against paper was the only sound in the room. Sukuna sat hunched over his journal, fingers ink-stained, spine curved as he filled the lines with quick, controlled strokes. His handwriting was sharp, slanted, perfectly ordered. A byproduct of a decade inside. Routine. Precision. Control. He always wrote after his sessions. Even if he hadn’t said much out loud, he needed it out. On the page. Honest.
Session Two – 4:00PM Spoke more today. She asked why I killed them. She didn’t flinch. She didn't moralize. Didn't run. Just listened. Wrote nothing. That’s how I know she was actually listening. She said she wants to understand me, not fix me. That’s rare. People always want to fix what they fear. She doesn’t fear me. Not yet. I wonder when she will.
He paused, pen hovering.
Then, slowly, he wrote:
She smells like clean soap and jasmine. Wore a green blouse today. I wonder if she knows it brings out her eyes. Probably not. Someone like her doesn’t dress for attention. She tries to disappear in her softness. I see her anyway.
He leaned back, the chair creaking slightly beneath him, he hadn’t eaten dinner. Didn’t need to. There was still a beer sweating on the windowsill, mostly warm now. The room was too quiet, too still—but he didn’t want to put on the TV. Noise felt disrespectful. As if he were trying to drown out her voice and her voice was still there.
In his skull. Precise. Careful. Every word weighted like a surgical tool.
“Do you want to take this seriously?” “What’s your goal here?” “I don’t plan to figure you out. I plan to understand you.”
Sukuna exhaled slowly, rubbing his jaw, fingers dragging along the slight stubble beginning to rise again across his throat.
She wasn’t afraid. She wasn’t naive either. She watched him—intellectually, yes, but also… emotionally and he could feel it. There was softness behind her professionalism, and he was beginning to crave it like oxygen. The distance between them was artificial. Temporary. He just needed to learn more. Close the space. He grabbed his phone. There were no social media apps on it. He didn’t need them. He had other tools. Older habits. Ones honed over years of watching the world from behind steel bars while the weak confused visibility with power.
He started with the practice’s website. Public-facing. Professional photo of her—of you. Smile restrained. Hair neat. Green eyes tired, even through the screen, he memorized the photo— then he opened his private server. It was an old dark net tunnel Toji had helped him set up, back when Sukuna was sixteen and angry at the world. He hadn’t touched it since before prison. But the skills hadn’t faded. Every firewall was a formality. Every privacy measure an illusion. First, he dug up the public licensing registry for mental health providers. From there, your full name, degrees, certifications. A few seconds more and he found your previous employment record—an academic hospital in Kyoto. He traced your old professional ID to a deleted blog.
He read every post.
Then your academic thesis—downloaded and printed.
Then your private Facebook. No photos since 2017. Locked profile. Not worth the effort.
But then—Instagram.
Private.
But your profile picture was current.
That was your kitchen.
Sukuna’s lips twitched faintly. Not quite a smile. He opened another window. Cross-referenced the subway map with timestamped check-ins from patients you'd tagged at your clinic. From there, he traced a pattern in your commuting path. Overlays. Geotags. One errant tagged photo from your friend—Shoko, he remembered her name from the front desk—showing your back as you reached to hang your coat by a brick-lined hallway.
He knew that building— low-rise. Ten-unit walk-up. West side. He pulled the city’s tenant registry. A few late-night clicks. One paid credit report spoof later.
Bingo.
Unit 3B. Your name on the lease. Updated just last year.
He leaned back in the chair again, rubbing his tongue against his teeth. That same slow burn building in his chest. It wasn’t lust—not entirely. It was possession. The creeping thrill of knowing something no one else did.
Knowing where you slept.
Knowing which window belonged to you.
Knowing the full name on your mail slot.
He closed the laptop, not because he was done—but because he was satisfied.
For now.
His hand slid across the journal again, fingers curling around the pen.
Found her apartment. Building’s secure. Cameras outdated. Fire escape on the east wall. Easy access from the alley behind the laundromat. Nothing threatening. Just observation—for now. She deserves to be known before she’s touched.
He tapped the period at the end of the sentence three times. A habit. A ritual. An echo of his own obsessive thread tightening. Then, beneath the line, he added—
She’s going to belong to me. Sooner or later. She just doesn’t know it yet.
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