Might be yandere

I'm still somewhat split 50/50 on if this guy (the one on the left on the front cover) is a yandere or not. He is possessive but I'm not sure how much of it is an act. I haven't read that many chapters though, so I would advise giving this a read and determining it for yourself.

I don't think I finished this even though it is quite short but from what I remember the grey haired guy is a yandere. Other people who have finished this manga have also recommended this on their yandere lists.

The brother of the blonde haired boy is definitely a yandere. He is not one of the male leads though I feel his character gets enough focus to satisfy your yandere cravings.

I haven't read this yet, but from what I've gathered, the black haired boy is the yandere but it's platonic obsession not romantic.