Project Seshin was an experiment that would create a copy of the last survivor of the Arisu Clan if he were to die while in his condition. This project was abandoned when the boy regained consciousness and was going to live again.
According to security tapes in the Eternal Testing Facilities, there appears to be a small boy wandering around, with blood red hair, black stained eyes, and a missing tongue...
Onee-san, where are you? Come out, Onee-san! Hehehe Onee-san, I'm tired of waiting around. Can we play now?
Oh Onee-san, who's that girl you're with?
She looks like a freak, with those horns.
Would she like to play with us?