Fuuzokugurui Desu ga Toshishita Danshi ni Kokuraremashita

Working in a bookstore, Azuma seems like a normal 30-year old employee. But privately, he's a hedonistic sex service addict who visits the brothel every day. One day he’s suddenly confessed to by his younger, calm and expressionless co-worker Robo-kun. Azuma refuses outright on the grounds that he's straight, but after discovering Robo-kun's super cute character gap, he kisses him jokingly and unleashes Robo-kun's other side!