Ariel Bellford was the second daughter of the baronet house of Bellford that didn’t have a single thing special about them. Three years had passed since her fiance Arsion, the successor of the ducal house of Hastings, became a knight and left her side. There’s a rumour that reached her ears, along with the news that Arsion is coming back, where they say that he is planning to become a Holy Knight! ‘I can’t let that happen!’ Ariel, who was agonizing on how she would be able to prevent Arsion from becoming a Holy Knight, ends up getting her hands on a s*x education book called, What to Do at Night. “Sion, I will teach you what to do at night.” A Holy Knight can only be a man who solely has a pure mind and body. Because of that, Ariel leads Arsion to the path of depravity and was planning to do it with him so that he can’t become a Holy Knight, but…… ‘But after this, what am I going to do?’ With regards to her problem, it was that Ariel also didn’t know well about ‘what to do at night.’