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 have yet to read this manga but what I've seen other people saying is that this yandere is a bit more open to interpretation. I'll edit my review once I get around to reading it, to add more detail. If I think it's a bit TOO open to interpretation I'll remove it from the list.
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.
I've read the first few chapters of this but I'm not sure if I'd really call the male lead a yandere as many of his 'yandere' moments are played for comedy and not really taken that seriously.
Page 127-144 defo yandere
Ch.5
has yandere moments, enough to for me to recommend giving it a read, but nothing really that extreme.
Ch.4
Silent Lover