The heroine “Mitari Yo” is an elite worker in a shoemaking company, the hero “Ishida Ren” works in a real estate development company. They are classmates in university and had a bet between them: the first to get married would receive a red envelope of 300,000 from the other before her 29th birthday...... They were sure that they couldn’t be a couple and the hero started to pursue the female junior worker of the company to win the bet. The heroine also met her ex-boyfriend again and this is how the story started....

One day, Sumire Iwaya stumbles upon a huge box in front of her house. Inside the box is a man. Later, she takes the man home and learns that his name is Takeshi Goda. Takeshi wants to live in Sumire's house, so Sumire suggests that he becomes her pet. Takeshi agrees and this is how they begin to live together....