For the first Valentine day ever Asu-chan has managed to make a chocolate heart. She can hardly wait for the moment to give her present to her beloved older sister and decides to pick her up at school. But to her big surprise she happens to observe Kyou also giving a chocolate present... to a boy, and then running away immediately! So Kyou has already someone she loves? Jealously Asu follows this guy to find out more about his character - and she learns that he has many friends, behaves friendly and helpful... in short: He seems just perfect. But can Asu hand over her sister to someone else so easily?
