Kai, the Super Bottom

From Renta!:

Shouma Yaku is the director and principal surgeon of Yaku General Hospital. He has it all: good looks, money, and status; and there isn't a single person who doesn't want him... Or so he thought. One day, a medical resident named Kai comes from Asakura Hospital on a study tour. With his mysterious allure, he starts stealing Shouma's lovers one by one...!! Yes, Kai is a super bottom. He lets everyone bang him, and yet he doesn't want Shouma. What's his motive...!? In the next story, "Ahh-ndo," a boss and his subordinate find each other a perfect match both at work and in private. In this office romance, rival staff members have to play dirty to succeed!