Ordinary teenager Kyohei Shinka and his disabled sister Shizumi return to their hometown Myowan, a fairly large coastal town in an unknown corner of Japan. Orphaned because of a tragic accident that had cost both of their parents’ lives, they settle in their elderly home which they had left four years ago. They reunite with their dear childhood friend Ayako Jogokoro and her little sister Sasa, and it seems like they had never left.Just as Kyohei thinks that their lives would go on as usual, he meets a mysterious girl, Yuma Atsuki, whose beauty is like no other. Although Kyohei does not have any memory of ever having met her before, she seems to know him. But how is that possible? What bonds does Yuma have with Kyohei and his sister? What dark secrets do her sweet, yet mischievous eyes hide? With the help of Ayako, Kyohei tries to fill in the blanks that are spread in this riddle. But then he discovers that the mystery enshrouding Yuma goes way beyond his own life, as two shady figures arrive in Myowan…