[kuromitsu]

I don't think Shun is untrustworthy, but I don't think it was a coincidence that he was the one who read the story about the boy who thought he was better than everyone else and ended up turning into a demon. Think about it, Shun is praised as one of the best students, as Forsaken_Infinity said above, there's something about him that indicates that he's special. And while he doesn't seem self-absorbed (rather, pretty humble) who knows what he really thinks. I wouldn't be surprised if with time this "specialness" would poison his mind... or there's also a possibility that due to him being better than everyone his relationships with other people would go sour, leaving him alone. I don't know if the demon should be taken literally or as a metaphor, but I think there's a good chance that Shun will turn into a "demon" when he's older.