Kamitori Yawa

A long time ago, around the time when gods and humans had crossed each others' paths, deep within the autumnal mountain recesses, Yamabushi, who was injured, requested help from a mountain god. The mountain god was wary, but gave him a place to sleep after being enticed by a sweet confection. However, the mountain god, who knew nothing of pleasure, let down his guard after the man had his way with him, and his horn, the source of a god's power, was broken. Yamabushi named the mountain god Suiren, and took him to the capital.

(Source: Kadokawa, translated)

Included one-shots: Yuusha-sama wa Kaikan wo Onozomi no You desu, Maou Senzoku Seitai-shi