Kenji Sato is a baseball player who initially played in America before returning to Japan to become Ultraman and continue his baseball career there. During a battle with a kaiju, he ended up becoming a single father to the kaiju's offspring, whom he named after its deceased mother. Now, Kenji must juggle life as a baseball legend and a single dad to a baby kaiju, striving not to mess up either role. He lives in a mansion with an underground bunker where the baby kaiju is cared by a robot nanny.