
I mean it has to be Jean. If the other two are involved im not sure how much or in what way, but there's no way Jean isn't the main culprit. There's too much evidence against him for it not to be. (I left a comment a bit further down marked as spoiler with a bunch of reasons)
Even in this chapter he insists on sleeping on the floor, then Eda 'sees' him there on the floor when the attacker comes in. But all he really sees is the blanket propped up indicating something is under the blanket. But we don't see a speck of Jean, just blanket. Like a classic, teen sneaking out and putting a dummy under their blanket so their parents think they're still home.
It's so obviously an alibi so Eda won't think it's Jean because oh look! Jean was in the room when the attacker was here so it can't be him!

Yeah that was the first dead giveaway and then everything that followed after was just piling on. Like the man doesn't even change his robes LMAO
He's been number 1 suspect since ch1 because they showed the hair and eyes.
Plus, in a narrative standpoint, he's the suspect that would be the most devastating to Eda since they actually have a long standing relationship.
Isn't it pretty much confirmed that it's the childhood friend? At least once they showed blonde hair and yellow eyes so it can only be him (at least that time, the other days could be the other guys)