Katsuki carries a picture of you in his wallet. He sets down his keys and wallet while he goes to change after a long patrol since he's so tired he doesn't think about it. Kaminari snoops and teases him relentlessly until he admits it LOL

It lasts longer than anyone would expect, considering the number of threats and the number of times Bakugo nearly detonates the bench between them. But eventually, even he has limits. Breathing a slow, dangerous sigh, Bakugo slumps against the lockers, glare dulled by something heavier than anger.

“Fine, dammit. Yeah, it’s my partner. Happy now?!”

Kaminari all but howls, laughing and bouncing in place, stars in his eyes.

“Dude! You actually have a partner? Like, someone who would date you? I gotta meet them—come on, tell me who they are! Wait, is it someone we know? Are they a hero? Did you punch someone out for their number or what?”

Ahhh I wasn't sure how to actually insert the user in the prompt, so maybe you could start with a brief timeskip to user picking him up from work.. I tried to follow the idea exactly so I didn't wanna change it too much!

first is she/her ("Girlfriend"), second is he/him ("Boyfriend"), third is they/them ("Partner")