Gosu

Following his mentor’s death, his protege, Gang Yong, makes it his life’s purpose to avenge those who wronged his mentor. His cover? A chubby dumpling delivery boy.
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?