The Kurusu family's homestay grows to three in the blink of an eye. Not yet accustomed to living with three monster girls, Kimihito's life is a series of disasters. When Miia sees Kimihito helping others, her jealousy boils over. With each girl loving Kimihito in their own way, they eventually come to blows!

Kimihito and friends venture into the woods to barbecue at Papi's request. The forest is an illegal dumping ground for industrial waste. Suddenly, Kii the dryad, protector of the forest, appears. Kii ignores Papi's attempts to stop her and uses her tentacles to grasp Kimihito. Kii is a monster girl who got lost after being kidnapped.