Touno Junna has a twin sister named Senna. He is an ordinary student at Sakurahama Private High School. However, in the past, a traffic accident deprived him of his parents and his memory. Junna survived the accident and since then, he lived only with his sister, though he's been looked after by his relatives.

His present life with Senna at the same high school is so pleasant that he can forget his severe past. However, Junna begins to recall the memories he lost in the accident. He enjoys the happy and pleasant days, but he is tossed by his past, his present, and his future. What is the truth hidden in his memory?

[Edited from Wikipedia]