The Undefeatable Swordsman

The son of a lowly innkeeper, Wumoon Song always dreamed of being a martial arts master, a dream that would never become a reality thanks to his frail body. Then one night, a mysterious guest leaves behind a painting as payment that enthralls Wumoon for reasons he can't explain. It soon becomes clear that it's no ordinary painting when Wumoon starts showing prowess in the martial arts he's never had before. Thus begins the path for a scatterbrained kid to change his destiny and become truly undefeatable!

(Source: Tapas Media)