Due to a clerical error, protagonist Kurusu becomes the host family to students of different species. One student, lamia girl, Mia, is touched by Kurusu's kindness, and makes bold moves on him.

Kimihito is suddenly kidnapped by Papi the Harpy. The naive Papi begins innocently bathing in public. Miia is jealous when she sees this, and the two get in a fight. Just then they hear the voice of a girl stuck in a tall tree... On another day, as Kimihito returns home from a shopping trip, a centaur girl leaps from around the corner and crashes into him. With massive breasts and a ponytail, Centorea was searching the town for a master to serve according to centaur tradition. In order to catch the man who snatches a purse right before her eyes, she chases after him with Kimihito riding on her back...

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!

A strange object appears in the pot and eats Miia! The culprit is an amorphous slime. Centorea weilds her blade against the attacking slime to protect Kimihito, but both of them end up covered in slime. They take a bath to wash the slime off, where they sink the slime on a wild rampage is search of water into the tub...! Papi names the slime Suu, and she begins living with them.

The girls' strategy meeting to protect Suu is interrupted by the sudden arrival of the Interspecies Exchange Security Squad. Believing they have come to capture Suu, the girls leave Kimihito and flee with Suu. Kimihito hurries after them and runs into a noble-looking girl in a wheelchair.

Miia trains to become Kimihito's bride by throwing herself into cooking. However, she seems absent minded and burns both of her hands. She is out of sorts because she is shedding. She cries that she is useless and can't even shed by herself, but Kimihito cheers her up and offers to help her shed.

Rachnea quickly becomes a member of the Kurusu household. Miia is jealous of her overly-friendly manner, but not even she stands a chance against Rachnea's mature composure. Centorea claims not to be opposed to living together, but when Rachnea's round the clock sexual tormenting of Kimihito doesn't stop, she can't keep her emotions in check!

Smith and Kimihito are on a date?! The monster girls borrow Suu's body to watch him, but when she becomes dehydrated she goes on a rampage. The monster girls fall one after another. Meanwhile, Smith and Kimihito move from location to location as they proceed with their date, eventually arriving at a love hotel?! Miia tries to enter the room, but Rachnera asks if she's prepared to witness Kimihito cheating on her...

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.

Unable to stand watching Kimihito and the monster girls go on dates every day, the MON members decide to go on fake dates with him. As Kimihito has a pleasant time with the girls who show him parts of their personality they normally keep hidden, a figure thought to be the culprit approaches them directly!

Lala the Dullahan explains to Kimihito that he is on the brink of death. Kimihito insists he isn't, but the monster girls buy Lala's story and do their best to take him to a safe place. However, despite their good intentions, their actions repeatedly put his life in danger.