A ghost locked in a room with a student who just moved into her apartment decides their only option is to solve mysteries together, one buried treasure at a time. The show treats each puzzle like it actually matters, then pivots into something deeper about why the GREAT 7 needed to build an island in the first place. Eleven episodes is genuinely not enough, but what's here moves with the energy of something that knows exactly what it is: a mystery-comedy that refuses to pick a lane and somehow pulls it off.

Disowned by his father, high school student Jugo Yama transfers to Nanae Island, an artificial island in the Pacific built by the genius group known as the Great 7 as a place where young people can pursue their dreams. Home to 100,000 people, most of them students, the island has prospered as a special student zone. Jugo expects to live alone, but his new apartment already has an occupant: the earth-bound ghost of Nanana Ryugajo, the Great 7's leader, murdered 10 years ago in a case never solved. Nanana reveals that before her death she hid items with strange powers across the island, known as the Nanana Collection. Hoping to find clues to her killer, Jugo searches the island's ruins with self-styled Master Detective Tensai Ikkyuu and her cross-dressing maid Daruku Hoshino, facing puzzles and battles of wits along the way. The show blends comedy, mystery and the supernatural.