That man is the strongest agent, "Jupiter." He was an invincible guardian in the devastated parallel world "B-side," but after 15 years of avenging his sister, he retires from being an agent. Hiding his superhuman powers, he lives a peaceful second life in the "A-side" at the age of 33. It was supposed to be peaceful... But with the appearance of a girl with a certain situation, the man's life turns into a "trial"! With a new name and a new family, he lives a strange life "under one roof." (Source: Kodansha, translated)