Chiyomi Horikiri (starring Yamamoto Maika), a third year high school student, grew up with the boy next door, Shunichi Minami (starring Nakagawa Taishi). They are childhood sweethearts. One day, Horikiri saw Minami with another girl and started to feel jealous. That night, Horikiri had a quarrel with her family and somehow shrunk to only 15cm. Just like that, Horikiri and Minami unexpectedly start a bizarre life of cohabitation....