Gakuen Shinshoku: XX of the DEAD

Fuente: AniList

Based on the erotic game by Syoku. Zombie Attack at School suddenly happened. With the tentacles behind them, zombies catch their prey one by one and make them zombies too. At this point all they can do is survive in school and find out about the zombies from watching their behavior. (Source: Nekopoi and Has Been Translated)