A high school student Mariko (Ando Sakura) is working hard at singing lessons in the choir as she aspires to become an opera singer. One morning on the way to school, Mariko is being harassed by some men, when she is rescued by their leader (Sasaki Takao). When she sees him on her way home later that day by chance, Mariko asks him by way of making things up to her to become her body guard on her journeys home. The two start to get to know each other, but he is reluctant to disclose his identity, and does not even tell her his name. Mariko visits him at home one day and finds out he is a Korean resident in Japan, called Sonmun. As Mariko herself shares the same root, the distance between the two rapidly closes. Sonmun, however, is trapped in the world of Yakuza, and is ordered to kill Mariko's father. On the day of the choir festival, Mariko's father is stabbed by Sonmun, but her feelings for Sonmun strengthen nonetheless.