BOX - Hako no Naka ni Nanika Iru

Seven people received a "puzzle" and ticket from an unknown sender, and followed the ticket to a strange square house. A mysterious woman who came "out of curiosity" joined them, and what awaited those people in the house was a girl as beautiful as a doll and maze beyond imagination. They cannot leave unless they solve the puzzle. When it's solved, part of your body will disappear! Can they escape? And, just who invited them there?

From Anilist