Since childhood, Tsukasa and his friends have loved mysticism and summoned various spirits for entertainment. One day, he found a spell that allows him to summon the wedding demon Rui. The ceremony required a broken mirror, a book, thread and scissors. As expected, nothing happened and he lived a normal life until he turned 18. At night, lying on the bed and about to fall asleep, he heard footsteps, and then he was pierced by a cold when someone hugged him from behind, he saw the clawed hands of a man who had a wedding ring on his finger. It was immediately clear that this was the wedding demon Rui, whom he had summoned as a child "Who are you?.. You're so cold..."