it’s been a while since i read it so i’m not exactly sure if it’s the one but it kinda sounds like this: https://www.mangago.me/read-manga/100_love_gage/
There is a side couple here that sounds almost exactly like that, try its ch 58...
https://www.mangago.me/read-manga/double_trap/

btw i can't remember much it was awhile back I read this......So they were side characters and there is this person who had black hair and whaat he does is collect and plays video games and never gone out (maybe sometimes he do )he found this game where he fell inlove with a character in that game. One day he met a person who had green hair and the green hair had a nasty personality you could say aggressive and the one with black hair delude to think he is just like the character he fell for because whaat I think green hair guy and the character had a similar apperanace to him just because of the green hair so he fell in love with green hair
I'M SORRY IF I EXPLAINED IT BADLY BUT PLSS TRY TO ANSWER THANKYOU!!