Takatsuki Souta has an introverted childhood friend who likes occultish literature. He consciously becomes aware of his interest/like of his friend and one day stumbles upon a mysterious bookstore. He finds a grimoire-like book and decides to buy it for his friend. She becomes cursed with lust and Souta must relieve this lust but must not cross a line that he later discovers when he seeks out the bookshop manager to try and dispel the curse. Warning: Lewd
This basically just ntr isn't it...
What is "ntr"?
https://www.urbandictionary.com/define.php?term=NTR
Here's a link friend.