Filthy
Summary: Zenitsu's other side doesn't seem half so bad
word count: 2.2k
i have been starving for some delicious competitive thunderbros content but couldnt find any. so i wrote it myself :D reader gets referred to with 'she' a couple times, but readers gender doesnt really matter not proofread because im lazy, so im sorry if theres any mistakes ;3 I hope you enjoy:D
“He’s disgusting.”
Kaigaku gnashed his teeth together, his eyebrows furrowed into a permanent scowl.
“He’s revolting.”
You watched how clench his fists, his shoulders tensing up as his nostrils flared.
“Trash like him shouldn’t be allowed to live.”
You looked like him like a deer in headlights, utterly clueless on how to respond to this tidal wave of contempt Kaigaku had for his sibling. The soft muttering of other voices in the small café filled the gaps of silence, along with the peaceful humming emitting from its speakers.
“There’s nothing about that sad sack of piss and wind that has any value to me.” He continued. “In fact, I’m nauseated by having to share the same house as him.”
You had no idea the mere mention of Agatsuma Zenitsu would have triggered this kind of outburst. Judging by his bodylanguage, you could tell Kaigaku and Zenitsu weren’t exactly on good terms, but still. The fact that Kaigaku could not bear to mutter at least one positive syllable about his other half left you bewildered.
“He’s pathetic. He’s a crybaby. He’s the furthest thing from manly to exist.”
The aroma of the steaming teacup in front of you managed to calm you down a little. The coffee Kaigaku had ordered remained untouched as well.
“Kaigaku…” you muttered. “What is your definition of manly then?”
He huffed in response, raising his eyebrows in such a cocky manner only Kaigaku could.
“A man.” He slammed his fist on the table. “Doesn’t beg girls to go out with them. Doesn’t blame others for their own shortcomings. Doesn’t take the easy way out.”
He let out a sigh, letting his spine collide against the cushions.
“Whatever. Let’s talk about something else. Speaking of that scum just makes my blood pressure go through the roof.”
You weren’t exactly sure how to feel about the project partner mister Himejima assigned you with. Zenitsu had mentioned once that Kaigaku had high scores, and whenever you managed to peer at his exam results, he was right.
Kaigaku strook you as someone disciplined. Serious. Dedicated.
Hopefully a breath of fresh air compared to other group projects where you yourself did all the work.
Zenitsu however, was not happy.
“YOU’RE WITH KAIGAKU????????????????????” He exclaimed, honeyed eyes blown wide as saucers by the news. His hand was desperately gripping onto your jacket, utter fear swirling in his eyes. “PLEASE TELL ME YOU’RE JOKING. PLEASE!!!!!!!!”
You sighed, gently putting a hand on top of his head like you always did. “Hey, it wasn’t like I assigned the group partners for this project. Mister Himejima did.” You rationalized. “Besides, Kaigaku doesn’t seem that bad to me. He has some of the best grades in our class, right?”
“ARE YOU KIDDING ME?????????????” Zenitsu wailed. “HE’S THE DEVIL!! THE DEVIL!!!!!!”
You sighed once more, trying your hardest to soothe his worries.
“It’s just us working together for this project. It really isn’t the end of the world.”
Zenitsu’s lip trembled. He reminded you of a sad, wet puppy.
You mindlessly grabbed ahold of the teacup in front of you, the warm liquid gracing your lips.
“Kaigaku.” You spoke, straightening your spine a little. “I believe you are entitled to your own opinion of Zenitsu. But please don’t insult my friend in front of my face.”
You were surprised to see Kaigaku’s posture relax a little. You had expected him to see your statement as a challenge, seeing it as an invitation to spew more insults at your face.
“Fine.” He said, leaning back. “Guess that’s fair.”
A short silence followed. A waitress walked by your table.
“Why are you friends with him, (__)?”
You blinked, letting a silence settle as you tried to come up with an answer.
“Because I like Zenitsu.” You replied. “He’s funny and kind. I love how loud and chaotic he is. He never makes a single day boring.”
Kaigaku’s eyes narrowed. You could almost see the flames of a bitter jealousy burning within them.
He hummed. “Tell me, has he ever tried hitting on you before? Begged you to date him even?”
You stayed quiet at that.
Kaigaku was right. You lost count of the times Zenitsu had gone on his knees, desperately clinging onto your clothes as he wailed and begged you to marry him.
The bitter chuckle emitting from Kaigaku confirmed his suspicion.
“I knew it.” He clicked his tongue. “But he’s dating that girl isn’t he? That second-year from the Taro class?” He tapped a spoon against his cup. “What’s her name again?”
“Nezuko.”
“Nezuko!” He laughed, repeating her name with great amusement. He smirked as he ran a hand through his dark hair. “Oh man. I cant believe all his begging and pissing himself in front of girls managed to land him someone.”
Kaigaku’s arrogance was dripping from his demeanor. He genuinely believed he was above him.
It was kind of attractive.
“But oh man. Everyone can see how utterly pathetic their relationship is. It’s been a year now and they never even held hands before. It’s hopeless. I almost feel bad for him. Even talking about it gives me secondhand embarrassment.”
You stayed quiet. Although something inside you itched to defend their relationship, you bit your tongue. Kaigaku wasn’t exactly wrong.
Nezuko was a good girl. Much kinder than anyone you’ve ever seen. But still, you’d be lying if you said their relationship wasn’t one-sided. Nezuko barely initiated any kind of physical contact, and from how busy the Kamado bakery could be, she often failed to reply to her texts on time.
You watched as Kaigaku suddenly leaned forward, a sly smirk etched onto his lips when he did.
“(__).” He almost purred your name. “Don’t you think you can do better?”
“I don’t know what you mean.”
“Look at you.” He said, finally taking a sip from his abandoned coffee. “I’ve seen you. Your grades are good. You’re smart. You’re disciplined. You’re pretty too.”
You tried your hardest not to look shocked. You hadn’t expected him to compliment you so easily.
“Aren’t you worried that guys like him end up dragging you down? Aren’t you tired of babysitting your supposed friend like that?”
You inhaled briefly, his constant slander now getting on your nerves. There was only so much you could handle.
“I think I can decide that for my own, Kaigaku.” You asserted. “Now, let’s just begin with the project.”
Kaigaku stayed quiet. You watched the smirk melt off his features as his green eyes bore into yours.
“Fine.”
——
Their kitchen smelled of steamed rice and vegetables as Jigoro scooped a handful of the food into three separate bowls. The two boys thanked him as he set down their dinner in front of them and began to eat.
Kaigaku watched as Jigoro and Zenitsu laughed about something he didn’t care about, reminiscing your company at the café. In a way, he kind of respected your assertiveness when it came to Zenitsu. Despite his constant slandering, you remained loyal and defended him as much as you could.
He thought about your body language, about your straightened spine and stern look in your eyes.
You had a backbone. He liked that.
He perked up as he heard a phone rang. Jigoro got up from his seat as he walked towards the living room, mumbling something along the lines of ‘I’ll go get it.’
A silence followed.
“Hey.” Kaigaku spoke, making Zenitsu look up from his dinner.
“That friend of yours. (__).” He paused. “She’s pretty hot. She single?”
Kaigaku watched in utter delight at how Zenitsu’s eyes widened in utter disbelief, his surprise quickly making way for vengeful, acidic rage. He chuckled when he watched the blonde’s hands grip his chopsticks til his knuckles turned white.
Veins of rage were throbbing atop his temples, his breathing quickened.
“Stay away from her.”
“Hah?” Kaigaku replied, enjoying every nano-second of ragebaiting Zenitsu. “Why do you care? It’s not like you ain’t got a girlfriend already.”
Although he’d expected a certain kind of annoyance about showing interest in Zenitsu’s best friend, he hadn’t expected him to get this enraged about it. Wide, unblinking eyes stared him down, mimicking a predator that looked ready to pounce.
He’d never seem him this furious before.
“You will not date her.”
Kaigaku clicked his tongue. “That isn’t your choice to make, asshole. She can think for herself.”
Even when Jigoro re-entered the room, it did not dilute the aggression plastered on Zenitsu’s face.
His eyes were glued onto him for much longer than he liked.
——
“(______________________________!!!” Zenitsu whined, pushing his face into the plush of your arm. You chuckled at the familiar feeling as you tried to get comfortable on your couch.
“Hold meeeee!” He pleaded. “My girlfriend is ignoring me AGAIN!!!!! I’M GOING TO DIE FROM A LACK OF ATTENTION!!!!”
You merely sighed, gently patting his head to soothe his emotions. He said that sentence way more often than he should.
You kept stroking his soft hair until his whines died down a little. He slid his arms around your arm, nuzzling it.
“Hey (__)…” He spoke. “How’s the project with Kaigaku coming along?”
“Honestly? He’s a much better partner than I expected.” You replied, smiling.
Zenitsu hated that subtle spark in your eye as soon as he mentioned him.
“He’s very disciplined and reliable. He takes a lot of initiative and takes his classes seriously. I like that.” You continued. “Besides, when me and him agreed to meet up at the Aozora café, he insisted on paying the bill. He even walked me home after!”
Zenitsu felt his stomach acid begin to bubble. You sounded way too positive about him. He hated it.
“Of course, we exchanged phone numbers to make communication easier. He even texted me asking if I got home safe. So far, he really exceeded my expectations!”
The smile melted off your face as soon as you saw Zenitsu’s horrified, disgruntled expression.
“Zenitsu…?”
--“But!” He pleaded, his grip onto your arm tightening. “But Kaigaku’s a brute!”
“I honestly didn’t get that impression…” you admitted.
The only thing that really bugged you about Kaigaku was how negative he was about Zenitsu. Although you stuck up for the latter like a proper friend, you didn’t want to sprinkle salt in an open wound. Perhaps Zenitsu was better off not knowing what he said.
“Besides..” You paused. “Do you really feel like that?”
Zenitsu sighed deeply as he let go of your arm, his eyebrows scrunched up in a sad expression as he stared towards your floor.
“No…” He sighed again in frustration. “Kaigaku…he’s a real pain the ass, but despite everything, I do admire him…”
You stayed quiet, letting Zenitsu speak.
“It’s like you said. He’s smart. He’s disciplined. He’s arrogant too, sure, but he always works hard. Harder than anyone else.”
His hands found your arm again.
“He never whines, never moans or complains. He always gets his work done properly and never makes excuses. If anything, he’s the real opposite of me…”
Your hand started rubbing soothing circles atop his head again.
“It’s alright.” You reassured as he locked eyes with yours.
“You’re still my favorite, Zenitsu.”
——
The following days, Kaigaku proposed meeting up at his place instead. According to him, the tables and atmosphere the Aozora café provided were no good to get any proper work done.
You agreed, seeing no reason as to why not. He did live together with your very best friend after all, and Jigoro was no stranger to you either.
How Kaigaku reveled in seeing Zenitsu’s sour expression as he opened the front door to let the both of you in. His keen eyes observed him carefully, taking in every detail about his tense body language.
That hungry look in his pathetic eyes. The way his teeth clenched and fingernails dug into his skin.
He loved it. Bathed in it. Pissing off Zenitsu was truly his biggest joy in life.
And so, what better method to aggravate him more than to be touchy with you?
Zenitsu noticed.
The way his filthy hands gently rested on your lower back, far too intimate for his liking. The way he leaned closer to you ‘because he didn’t quite catch that’, and finding other bullshit excuses to get closer to you.
The times he called you ‘pretty’ were the times Zenitsu was ready to fly off the handle. His nails dug violently into whatever he held, trying to calm his racing heart as it vibrated against his ribs.
Of course, Kaigaku remained gentle, never going as far as to make you uncomfortable or afraid. After the dreaded study-sessions were over -which Kaigaku insisted on doing in their living room, the scene of you two bonding all too painfully clear for Zenitsu to see- he insisted on walking you home, always texting you if you got home safe like the true gentleman he was.
You couldn’t help but think about him sometimes. Although you audibly despised and disagreed with the way he badmouthed Zenitsu, there was something about his overbearing arrogance and carefree attitude that clung to you. Something enticing about that overbearing sense of self.
You were almost sad when the project was finished. Although you’d never admit it, part of you felt like the whole trajectory ended way too quickly.
Two eyes widened in surprise as soon as the grades were published. A gratifying score of 90/100.
“Hey.” Kaigaku’s low voice spoke as his teal eyes registered the grade. “Let’s work together again sometime soon.”
You nodded, smiling.
“Sure.”
