The Undefeatable Swordsman is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

This is the story of Song Woo Mun. The village Inn owner's son, Song Woo Mun is weak as a young boy, whose condition only when he suffers a loss of his intellect, due to the Sansu-hwa, a painting gifted by a Sage. But unbeknownst to everyone, his life is about to change, and a new destiny awaits him, when he turns 20. Not only does he undergo an awakening, but he also sees the Undefeatable Flower blooming in the painting. What could all of this mean for Woo Mun? And what strange world awaits him?