Hwansaeng cheonma

After defeating all the enemies of the Murim Alliance, the Demonic Alliance and the internal enemies; Chunha Jin, the master of the Murim Alliance who held the title Strongest Under Heaven brought forth peace to all of Kang Ho. But one day he dies unexpectedly.
Once he openes his eyes, he is in a body of a twenty year old youth named Byuk Lee Dan. How will the man who once held the title Strongest Under Heaven live this new life? And what will his death entail to Kang Ho?