The Demonic 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.nl fastest updating comic site. The Summary is

“Warriors are not born—they are made!” Ryu Seong was kidnapped as a child and raised to become a warrior for the Demonic Cult. After years of grueling training, he was finally recognized as an official warrior. But during a trial, where many of his comrades fell victim to a deadly poison, Ryu Seong discovered something extraordinary about himself—he was immune to even the most lethal toxins. This revelation set him on a journey of self-discovery. Believing that the scar on his chest, the one hindering the flow of his internal energy, might hold the key to his true identity, he chose to vanish from the world. Now, Ryu Seong lives in quiet seclusion, seeking answers to the mysteries of his past and the wounds that define him.