Ryuugajou Nanana no Maizoukin

The Pacific Ocean's Nanae Island, a man-made island, is equipped with everything needed for children's education and training. It was developed by the Great Seven, a band of intrepid travelers led by Nanana Ryuugajou, as a location for young people to pursue their aspirations. Juugo Yama, a high school student, arrives on this island after being banished and abandoned by his family. He is relieved to be free of his father at last. He moves into his new chamber and finds the ghost of Nanana Ryuugajou, who was imprisoned on the island following her unsolved murder ten years earlier. Juugo learns from Nanana that, just before she passed away, she hid a collection of objects known as the Nanana Collection—items with special and enigmatic abilities—all over the island. With the assistance of Tensai Ikkyuu, who calls himself the "Master Detective," and her transgender maid Daruku Hoshino, Juugo embarks on his investigation in the hopes of uncovering information that may lead him to the person responsible for her death.