Amamizu-kan is an all-female boarding house occupied by The Sisterhood, a group of geeky otaku women who have a fierce dislike for people they refer to as The Stylish and men in particular. The newest addition to the group is Tsukimi, a shy, socially awkward girl with a fanatical passion for Jellyfish. When Tsukimi unwillingly meets one of The Stylish, a sassy girl at her local pet store, her discomfort is magnified when Tsukimi discovers that her new friend is actually a male named Kuranosuke. Kuranosuke, the son of a powerful political family, is strangely drawn to Tsukimi and The Sisterhood. Here he is introduced to Mayaya, who is obsessed with the Three Kingdoms Jiji, who has affections for old men; Banba, who is a train fanatic; and Chieko the landlady who loves dressing in traditional Japanese costumes. Kuranosuke is eager to win them over, however, only Tsukimi knows his true gender. When Shoko Inari, an evil land developer, begins to target Amamizu-kan's place of residency, Tsukimi, Kuranosuke and The Sisterhood band together, to save their way of life with humorous results.