For generations, the Kagurazaka family has possessed a unique skill - the ability to communicate with Inari's messengers. This ability has been preserved through trading matrimonies with the Ujou women. Rio is the current recipient of this gift and has been eagerly awaiting his prospective spouse's arrival, only to be shocked when she elopes with someone else. In the aftermath of this experience, Rio is taken aback when Nagi, his intended's younger sibling, arrives and asserts that he is capable of filling her sister's shoes, stating, "Even if I cannot father children, I am proficient in sexual intercourse."