How about Kelly being insecure in his relationship with Matt, wondering if he’s being a good boyfriend, is Matt really happy with him etc?
Summary: Five years into their relationship, Kelly Severide begins to struggle with quiet insecurities—wondering if Matt Casey is still happy with him or just staying out of routine. Matt, now a Captain, has been acting distracted and distant, causing Kelly’s anxiety to spiral. What Kelly doesn’t know is that Matt has been secretly planning a proposal. When the tension finally breaks, Matt gently reveals the truth and reassures Kelly that he still chooses him—every day. What was meant to be a surprise becomes a moment of honesty and comfort, deepening their bond even further.
There were parts of loving Matt Casey that always came easy.
The way he brewed coffee with enough strength to wake the dead, left post-it notes on the bathroom mirror when he had an early shift, or how he reached instinctively for Kelly’s hand when they walked through crowds. There was ease in the familiarity—living with Matt had become second nature, like breathing or driving or knowing just how many steps it took from the bedroom to the kitchen in the dark.
But still, Kelly Severide’s brain—especially on days when the house was quiet and the shadows got too long—had a way of turning on itself.
It started with nothing. A canceled dinner plan here, a distracted nod there, Matt’s phone lighting up with texts from Sylvie or Boden or someone from HQ that he never bothered to explain. Just a few too many nights of Matt staying a little later at the house, or coming home with that particular look in his eyes—the one Kelly used to see after Gabby left. The one that said he was carrying something alone.
Kelly never wanted to be that for him. Not the weight. Not the problem.
He hadn’t said anything yet. He wasn’t sure he should. But lately he found himself lying awake even when Matt was snoring softly beside him, staring at the ceiling and wondering if Matt still looked at him the same way. If the warmth had faded into routine. If he was still enough for someone like Casey, who always carried himself like he belonged in the light.
It was a Tuesday. A nothing kind of day. Firehouse 51 had cleared two calls before noon, and Severide had retreated to the lounge to nurse a minor ankle sprain from an awkward dismount. He wasn’t hurt bad—just sore and in no mood to talk. Capp had made a dumb joke, and even Cruz hadn’t managed to get more than a grunt out of him.
That was when Matt walked in.
“Hey.” Casey crossed to the couch and crouched down, eyeing Kelly’s leg. “Still hurting?”
Kelly nodded. “Nothing serious.”
Matt sighed, brushing a hand over his hair. “You know, you could say more than three words to me.”
Matt’s brow furrowed. “What’s that supposed to mean?”
Kelly stood—too fast—and winced, biting out, “It means you’ve been distracted. You’ve barely looked at me in days.”
Matt blinked. “That’s what this is about?”
Kelly folded his arms. “You tell me.”
Matt looked around, clearly flustered. “Look, maybe we should talk when we get home.”
“I don’t want to talk later. I want to know now. Are we okay, Matt?”
The question landed with too much weight. Kelly’s voice had dropped, quieter now, laced with something vulnerable he rarely let out around the house—especially not at work.
Matt’s mouth opened, then closed again. And Kelly watched it happen—watched him go through the calculus of what he could say without letting the cat out of the bag.
Because yes, Matt was distracted.
He’d been coordinating a proposal.
Not a flashy one, because Kelly hated public declarations. Something simple. A night at the lake house, steaks on the grill, that quiet brand of peace they only ever found there. He’d picked up the ring three weeks ago. The little black box was currently hidden in the back of his sock drawer, tucked beneath a stack of department T-shirts. He’d been talking to Boden about time off, whispering to Sylvie about logistics. Trying to be discreet.
But now Kelly looked stricken. Hurt.
And Matt realized with a surge of guilt: in protecting the surprise, he’d forgotten to protect him.
“Kel,” Matt said softly, reaching for his hand. “Come with me.”
They slipped into Matt’s office and shut the door. The fluorescent lights buzzed faintly overhead.
Matt turned to face him. “I’m sorry. I didn’t realize I’d been making you feel that way.”
Kelly was still standing stiffly. “You haven’t been home much. And when you are, it’s like you’re… somewhere else.”
“I know,” Matt admitted, rubbing the back of his neck. “And I’ve been trying not to say anything because I wanted to surprise you, but clearly this isn’t working the way I thought it would.”
Kelly frowned. “Surprise me how?”
Matt took a breath, then exhaled. He didn’t pull out the ring, but he didn’t hide anymore either.
“I’ve been planning to propose.”
Matt continued, voice gentle. “I’ve been trying to get everything lined up—time off, the right setting, the ring. I wanted it to feel like us. But I didn’t think about how me being distracted might mess with your head. I should have told you sooner.”
Kelly didn’t answer right away. He sat down heavily on the edge of Matt’s desk, rubbing his hands over his thighs. “You were going to ask me to marry you.”
“I am going to,” Matt corrected. “I still want to. This just… isn’t how I meant for you to find out.”
There was a long silence. Kelly dropped his head into his hands, breathing deeply. “I thought you were pulling away. I thought maybe you were realizing I’m not…”
“Not what?” Matt’s voice was quiet but firm.
“Not easy. Not good enough. Not what you want long-term.”
Matt crossed the room slowly. “Kelly,” he said, kneeling in front of him again. “You’re not easy. I’ll give you that.” A flicker of a smile. “But you’re everything I want. You’ve been it since the day you brought me coffee and argued with me about hose pressure in front of Boden.”
That pulled a snort from Kelly. He looked down at Matt—his captain, his partner, the man who still made his heart stutter after five years.
Matt reached for his hand again, holding it tight. “I wanted to wait for the perfect moment. But maybe the perfect moment is when you need to hear it most.”
Kelly’s throat worked around a knot of emotion. “I still don’t know why you chose me.”
“Then let me keep showing you.”
That night, back at the apartment, Matt pulled Kelly into his arms as soon as the front door closed.
No ring. No speech. Just a promise, whispered low:
“Still choosing you. Every day.”
And finally, Kelly let himself believe it.