Tensei Dai-hachi Ouji no Shiawase Kazoku Keikaku

The eighth prince of the Valte Kingdom, Rieto, vaguely recalls a dream of being a salaryman while in a coma after nearly being poisoned. He also remembers a dream of building a happy family, but as the insignificant youngest prince in a household rife with brutal succession disputes, it seems unlikely he’ll ever achieve that dream. Having quickly given up on this family, Rieto vows to work hard to build a happy family of his own. Yet, for some reason, he starts getting involved with his older brothers, who were supposed to be his deadly rivals…? “I’ll build a happy family with a cute wife and adorable kids!” The story begins with the protagonist at age five.