The Nanae Island Third High School Adventure Club

Juugo picks up a jewel that fell from the sky as he was on his way home from the convenience store. It turns out to be one of Nanana's Collection: the The Eye of Yuguthos. Juugo is shocked that Nanana's Collection really exists. Meanwhile, the master detective Ikkyuu Tensai and her assistant, Hoshino Daruku, pay a visit to room 202 of the Happy House in search of the stolen jewel.