Unrivaled Warrior 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

"Don't underestimate a guard! You might end up dead!" It’s been four long years since Yunbi was tricked by his master into becoming a disciple of Kwon Dalmun. Training in the unconventional "Geonwoo Divine Art", which requires physical impact to channel inner energy to the dantian, Yunbi has grown tired of the absurd methods—falling off cliffs and crashing into trees to build up his strength. After finally inheriting all of his master's inner energy, Yunbi returns home, only to be pressured by his mother into taking a job as a gatekeeper (known as a "Wisa") at the Martial Alliance’s main gate. Despite being mocked by martial artists and frequently provoked into fights, something strange happens—every hit he takes channels energy into his dantian, gradually increasing his internal strength! To make matters worse, the peculiar moans Yunbi unconsciously lets out when struck only fuel misunderstandings across the martial world.