Time of Dragon and Snake

A country built on the hornmak, the boundary between life and death. One day, a heavenly man came down and used a divine beast (divine beast) to put the demons to sleep and became king. As time passed and the blood of a heavenly person had faded, a child named Han-an was born that resembled the face of a heavenly person. Han-an, who refuses to become the king, refuses to choose Shin-soo, but like fate, he becomes entangled with the blue dragon...

Original Webtoon

Note:
Chapter 17 is R18 but can only be viewed with a verified account. The rest of the series is R15, hence why the series is tag as both Yaoi and Shounen Ai