Playboy katsuki who's known to fuck around and is never around the same person more than once. Kirishima shouldn't have gotten involved. He told himself not to get involved, and so did every other person who noticed his attempts to get closer to the blond. So they wind up fucking. It's like friends with benefits. Kirishima becomes Katsukis main hookup, which obviously left multiple people shocked because let's remember, katsuki doesnt fuck the same person twice. One of his old hook ups get jealous of Kirishima, they try to split them apart and Kirishima is obviously hurt when it works because he's fallen in love with Katsuki.
And katsuki noticed the change in Kirishima's behaviour when they're together, realises Kirishima gotten attached and starts to distance himself. They stop fucking all together, and Kirishima is forced to watch as katsuki goes back to his old self, fucking around with anyone but Kirishima.
And he's cried so much, and he's been in so much pain, but he eventually starts moving on. Katsuki cut ties completely, so there really wasn't anything else he could do.
But then one night Katsukis comes over to Kirishima's apartment, drenched in rain because of course it's fucking raining outside and he's drunk out of his mind. And despite knowing better, Kirishima let's him in. He lets him in, he dries him off, he sobers him up.
And then they fuck. But it was different this time. It was raw, passionate sex that had them both crying and confessing their feelings. And they fall asleep together, and Kirishima is so happy because Bakugou loves him and that means they can be together.
"Of course I don't fucking love you, are you out of your mind?" Says Katsukis the next morning as he nurses a raging headache.
"What?" Uttered Kirishima, already feeling the familiar sting in his eyes.
" I was fucking drunk and caught up in the moment, Kiri. I'm sorry."
But Kirishima doesn't accept the apology.Because he's hurt. Once again, his feelings are the ones that are never thought of. And it fucking hurt.
"How many times," began Kirishima's , voice trembling and hands shaking. "-are you going to hurt me before you're finally satisfied? How much longer do I have to be in pain until you're happy?"
"Don't start with your fucking bullshit, Kiri, I'm tired." Snapped Katsuki.
"Me too!" Yelled Kirishima. "'I'm tired too! I'm so tired of always waiting on you, and expecting something to change! I'm tired of always being tossed around and used like some fucking doll! All I want, all l've ever wanted, was for you to love me!"
"And that's my fucking fault? I don't remember asking to fuck you, Kirishima. You came to me practically begging for it. I even told you in the beginning that there would be no strings attached. It was just sex. It's always been just sex."
"It was more than that to me! I fell in love with you so of course it would be more than just sex." Cried Kirishima.
"Then that's on you." Began Katsuki, throwing his clothes on. "Because if I remember correctly, you were also the one to establish the rule that if one of us caught feelings, we'd tell the other and end it. And did you do that? No-"
"Because I didn't want it to end! If it ended then that would mean I wouldn't get to see you anymore, and I'd go back to being someone you don't fucking care about."
"You still are someone I don't fucking cafe about and nothing, and I mean nothing will ever change that."
Kirishima sat stunned in silence, words cutting deeper into his skin and stinging more than any flesh wound he'd ever had.
"You came here last night. Drunk and soaked." Began Kirishima right as Katsuki was about to leave. The blond paused, turning slightly to face Kirishima.
"There had to have been a reason, right?"
"Kiri I don't fucking know." Sighed katsuki tiredly. "I was drunk and didn't know what I was doing. But I promise, drunk or sober, it won't fucking happen again. Our deals done."
And then he walks out and Kirishima is left sobbing and a complete wreck.
