I’m sure Emma didn’t killed the Professor because Emma is not that type of person who will hanged the target, she’s more like a knife killer than a smarty killer, and Yohan never mentioned Emma killed the Professor, so that means the murdered is still unknown.
Yohan and Elios hadn’t met each other at all, he thought Elios existed as well because he believe what Emma says (You know because of her split personality, she’s Elios and Sarah) and he taught Elios is avoiding him. But did you see some of the chapters that Yohan and Elios hadn’t met at all.
(I’m sorry!! I’m not really good at english nor explaining the situation >///<)
I reread it an just realized you're right. I must have been thinking of that time in the abandoned house and now that I think of it the other guy that works at the cafe with her said emma was weird. So I'm wondering if its because she's always talking to elios who isn't there and it creeped the guy out ╮( ̄▽ ̄)╭
Im confused about something tho if the real elios died one year before the events of the present story how do you explain the first season I guess u could blame it on emma being delusional but if this yandere elios is just her then how would you explain elios interacting with people like at the cafe, if they were talking to emma all this time why would they call his name or the fact that yohan has seen elios or him taking her on a date or him taking care of her when she was sick. And who killed the professor