Chiyo, despite her normally calm demeanor, is easily worked up. Cute things make her pull all-nighters to pursue cuteness. Ninja-related things remind her of her ninja upbringing.

Sekine invites Chiyo to a sleepover at her house, and the other two invite themselves as well. They deepen their bond while Rikka learns more about the quirky cultural activities that take place on Earth.

Fuku-chan, Rikka's new space alien pet, has gone missing, and he's not just a harmless walking giant mushroom. Can Sekine stop him from devouring her friends, both figuratively and literally?