Attempts to find responsible adults lead to deadly booby traps.
Upon recovery, he finds himself in the principal's office, now the safe room of Class SSS, Yuri's group.
He is introduced to all the members, and introduces himself as Otonashi, but can't recall his given name.
TV Tropes tells me that Everyone Is Jesus In Purgatory is an overactive imagination searching for Deep Meaning in everything.
The show summary tells me it's intended to be purgatory.
Let's see how it goes.