かつては最強無敵の勇者様 ～姫には内緒のレベルダウン生活～, Once the Strongest and Invincible Hero: A Level-Down Life Kept Secret from the Princess!, 한때는 최강 무적의 용사님 ~공주에게는 비밀인 레벨 다운 생활~, Antaño el héroe más fuerte e invencible: ¡Una vida de nivel bajo en secreto para la princesa!, Cựu Anh Hùng Vô Địch Thiên Hạ: Cuộc Sống Tụt Cấp Bí Mật Trước Mặt Công Chúa!

The middle-aged hero, Juurouta Hoshino (Juro), successfully reincarnated into another world with a mountain of cheat abilities. Although he safely defeated the Demon King, he now faces a crisis where his level is gradually dropping! Crying out, "I have to survive somehow!" he attempts to ingratiate himself with the royal family for self-preservation. As a result, for some reason, he ends up in a situation where he has to live together as a "temporary married couple" with the beautiful princess, Stella, who is supposed to be his overseer...!?