Nao is the third daughter of Daisuke Sendo, a wealthy man, and the daughter that Daisuke had his mistress give birth to. According to the will of Daisuke, who died suddenly, she was entrusted with the business of the Sendo family along with her fiancé Atsushi, but due to the scheme of her half-sisters, she was confined to her villa and trained as a slave. It was
