ゾンビの同級生はプリンセス -不死人ディテクティブ-

Aruba and his classmate who was also his childhood friend were kidnapped and in the struggle to escape, he died. However, he has come back as a zombie in order to find the person who killed him! However, he has no idea where to start but one day he meets Ruuna – a girl claiming to be an immortal demon princess who agrees to help him find the murderer as long as he becomes her slave! He reluctantly agrees and they set up a school club in order to find villans and Ruuna will punish them with her mystic sword. Will the pair ever find out who murdered Aruba?