Akira Toudou, a high schooler living in northern Okinawa, lives peacefully with his mother and his older sister, Haruka. However, behind their peaceful life lies a secret passed down through their family: Haruka has inherited a mysterious power from their father, known only as "Engine," and she has lived her life hiding this power from others. Akira, however, inherited nothing. He harbors an inferiority complex due t...