The story focuses of Okojo-san (a ferret?) who lived in the northern mountain. It got caught by a kid and sold to a pet store. Lucky for Okojo-san, after going through a lot of hardships, he managed to escape the pet store and end up in Tsuchitani's room.
Tsuchitani is a college students who is not very sociable and quiet. Although he's poor, he decided to keep Okojo in his place. Staying in Tsuchitani's room, Okojo meet a rat owned by a female cartoonist who lives in the next door. Okojo also meet Saeki Tomo, Tsuchitani's friend's younger sister, who tried to feed him a pudding (ferret is carnivore ;b). And, What's next?