High schooler Odagiri Momo leaves her home island to attend high school on the mainland. Having grown up on a boring island, Momo dreams of becoming a detective and is always on the lookout for cases. After moving into her first apartment, she meets the mysterious beauty Akaishi Kotone and falls for her at first sight. Declaring she'll make the reluctant Kotone her “assistant” against her will, the two form a buddy team to solve small everyday mysteries together.