Nanana's Buried Treasure

Juugo Yama moves to a special student island after being disowned by his father and rents a cheap room only to find it already occupied by the ghost of Nanana Ryuugajou, a girl murdered ten years ago who cannot move on until her killer is found. Nanana spent her life hiding powerful treasures across the island inside deadly ruins, and Juugo begins hunting them to fund his investigation. The series combines puzzle-dungeon adventure with a quirky cast and a mystery that slowly reveals deeper conspiracies.