huhu

hey guys, I'm looking for a manga that I read once and it's a bit old, maybe from 2014 or 2016/18? And it was a whole series of mangas with the same students and each couple had their own volume and the first volume was a couple with the head boy and an old friend who is useless and they fall in love anyway, the head boy becomes weak and there's a scene where they're in a special building at school and they get closer... does that mean anything to you and do you know which manga I mean? I think it also starts with N or K?