Akira Toudou, a high school student residing in northern Okinawa, leads a tranquil life with his mother and older sister, Haruka. Yet, concealed beneath this calm existence is a family secret: Haruka has inherited a mysterious power from their father, referred to only as "Engine," and has spent her life keeping this ability hidden from others. Akira, by contrast, inherited nothing. He suffers from an inferiority complex stemming from his own weakness. Subsequently, strange events began to unfold across the globe. What is the objective of the unknown enemy closing in on Akira and his friends? Now, with the fate of the universe hanging in the balance, a brother who possesses nothing and a sister who possesses everything must discover what they can truly accomplish together.