The Secret to My Silky Skin

Ryota, a boy who lives with his parents in Kyoto comes to Tokyo for a business trip and stays with his fuck buddy, Issei.
They have no special plans for the five days together. They will go to work in the morning, come home, spend the evening together, and sleep. The first night when Ryota arrives, Issei starts to have sex with Ryota just as usual, but Ryota is somehow unable to respond. In fact, Ryota has been concerned about a certain thing since before he visits Tokyo.