Rumiko Iwashita is the homeroom teacher for students Riko Mikogami, Rimu Mikogami, Ken Inomata, Tamao Kijima, and Kanon Hatori, overseeing their class activities and educational development. Her story develops a romantic relationship with Kabaya Popota, a member of the Animalian Fang Gumi possessing hippopotamus transformation abilities. Despite Kabaya's affiliation with the Animalian group, Rumiko is spared transformation, suggesting a protective bond or affection between them. Their relationship progresses, culminating in marriage by the series finale. This marriage signifies a connection between the human world and the Animalian characters.