Reina, the princess of the Kingdom of Fromesia, has always been looked down on as an illegitimate child amongst royalty. As part of an agreement to maintain peace between two kingdoms, Reina is sent in place of her stepsister to be married to the prince of the kingdom of Beastmen. On arrival, Reina expects to be welcomed by Prince Cain, rumored to be fearsome and almighty. However, the man who appears before her is anything but! With shining golden eyes, delicate charm, and an emotionally mature demeanor, Prince Cain welcomes Reina to his domain, and the wedding proceeds without a hitch. However, as they meet for their first night as husband and wife, Prince Cain states that this marriage is only for current circumstances and will only be temporary… what could he possibly mean…?