I'm waaaaaay late to this, but I'm inclined to think the culprit is Enbi. Originally I thought that because Yui hadn't identified a body as belonging to him, so I thought maybe he was somehow under the bed pretending his head was severed.... (it's Danganronpa, that could totally happen)
But from his behaviour, it seemed as if he was limping or having some trouble walking, and we know from chapter 2 that the culprit had to relearn how to walk after his injuries, and he struggled after getting woken up for more investigating (though that could be due to the sleeping drugs). It's also worth noting that he wears sunglasses in the middle of winter, which could be to conceal his eye colour if it differs from the real Enbi's. Inuzuka was likely the detective who investigated the arsons and the real culprit behind them, based on how he went on about astronomy and how much he likes to impress people by flaunting his research and pulling a Sherlock on Yui, he probably has something of a hero complex. Amino was just another innocent like the real Enbi.
no subject
But from his behaviour, it seemed as if he was limping or having some trouble walking, and we know from chapter 2 that the culprit had to relearn how to walk after his injuries, and he struggled after getting woken up for more investigating (though that could be due to the sleeping drugs). It's also worth noting that he wears sunglasses in the middle of winter, which could be to conceal his eye colour if it differs from the real Enbi's. Inuzuka was likely the detective who investigated the arsons and the real culprit behind them, based on how he went on about astronomy and how much he likes to impress people by flaunting his research and pulling a Sherlock on Yui, he probably has something of a hero complex. Amino was just another innocent like the real Enbi.