Everyone thought you were dating Katsuki, but you weren't, much to everyone's surprise and disappointment.

Of course, you had a boyfriend.

The problem was, your actual boyfriend barely acted like a proper boyfriend and it was Katsuki who, despite being your friend, acted like a lover to you, without the title. Whatever it was that your boyfriend should be doing, Katsuki ended up doing.

Did he had complaints? Absolutely not.

It was selfish of him, acting like a boyfriend to you when you were merely friends, but he couldn't help his feelings for you even if you were oblivious to them and dating someone else. Selfish of him, trying to fulfill the fantasy of you being his when you weren't.

It wasn't his fault your boyfriend was absolutely useless, but that didn't meant he wouldn't take advantage of it.

He'd take any opportunity to do what your stupid boyfriend wasn't doing, maybe then you'll notice he was the better choice for you and finally ditch that dumbass.