Gosu

Gosu (The Master) is a webtoon, by Ryu Ki-Woon and Moon Jung-Hoo, that is published on Naver and LINE Webtoons.

Plot
A young man set forth to avenge his master, a once powerful martial artist who was betrayed by his own men and barely escaped with his life. Armed with his master's supreme martial art techniques, he is ready to bring terror and wreak havoc among the Murim. But before he even got started, he learns that the ones who had betrayed his master are already dead... Erm, so what happens now?

Official

 * Naver (Korean)
 * LINE Webtoons (English)