Ttangeul Samkin Bi

Three hundred years have passed since the dragon and the serpent vanished. The Heavenly Emperor, who had worried about the human realm, commands the last dragon, Yeonmok, who had gone into seclusion after the death of his beloved disciple, to find the whereabouts of the dragon and the serpent. Descending to the human realm, Yeonmok encounters an enigmatic young serpent named Doya...

(Source: Ridibooks, translated)