Ah, the dream of 13! Kouta is our normal everyday boy, living with his fun-loving workaholic father. Lusting after the school idol in his class, playing games with his friend, there's nothing especially noticeable about him. But one day his father has to transfer to Sapporo for a time and mysteriously appear a girl who volunteers to be Kouta's live in caretaker. And what a girl! Everything about her is mysterious: her mysterious incredibly showy body, her mysterious interest in our boy, her mysterious need to sleep in the same room... Doki, doki...