Roumantei no Juunin

From Attractive Fascinante:

Sakuya, a high-schooler, went to a place called Romantic Villa Hakuou to look for Shinonome to fulfill his grandfather’s final wish. This is a place where only those with power and money can come to buy a man’s night. Shinonome is the most beautiful and the number one oiran there. Sakuya had wanted to leave once he settled the issue. However, he was forced to stay because of Shinonome’s stubbornness. And that night, he witnessed the number two oiran, Asagi, serving his benefactor. What will he do from then on?