In 2119, the spaceship Green Sleeves found 3 planets attacked by X23, a moving planet heading Earth. The Earth government ordered Green Sleeves to attack X23, but Dr. Sugita, the captain of Green Sleeves, refused because he believed they could co-exist. Then, the communication with Green Sleeves was cut abruptly... In 2121, Susumu, the son of Dr. Sugita, is visited by strangers. The take him to ...