Explanation is needed at the end of Corpse Party - Tortured Souls OVA I can't figure out what's going on at the end of episode 4 of the OVA. When Satoshi, Naomi and Ayumi finally preparing the ritual to go back to their own world, Satoshi told Naomi that he knows she took other person's paper scrap. Then, he gave her his paper scrap because he had Yuka's (his sister) one.



And then, at the final scene, they made it without Satoshi. What's wrong here? If they can't use other person's paper scrap, then why Naomi still alive? Wait, I guess they can use other person's paper scrap but can't use deceased one (like Satoshi use his dead sister's one)? If so, does Satoshi purposely sacrifice himself to let Naomi escape? It's confusing though, well, I watched the OVA but didn't played the game before.
Finally found a screenshot of the other student's ID.



Satoshi was using Yuuya's scrap, not his sister's; this resulted in his death on trying to return to his world. This is due to Yuuya not being a part of the ritual that Class 2-9 held, so his scrap could not bring Satoshi back.