Based on Konami's mobile game Jikkyou Powerful Pro Yakyuu, this four-episode sports ONA centers on a boy who enrolls at Powerful High School with his heart set on becoming a baseball player. There he meets Subaru Hoshii again, a childhood friend he once vowed to play alongside at Koshien, the summer tournament for high school teams. Subaru, however, appears to have no memory of that vow.