High school student Mariko sings in the choir at the all-girls school she attends, and her biggest dream right now is to go to a music college. One day on her way home from school, she accidentally drops her bookbag into the sea. A man jumps into the water and recovers the bag for her, but all of her score sheets have been ruined. From that day on, Mariko’s new acquaintance becomes her bodyguard, walking her home everyday. But for some reason, he refuses to tell her his name.