SSS-Class Assassin’s Return 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

In the turbulent world where the game ‘Moyu Conquest’ has crossed into reality, Mo Bei, a leading figure in the human coalition, repeatedly led his team to eradicate demon lords capable of endless resurrection. However, during one battle, both the demons and humans lost their top fighters simultaneously. As a result, the blood of the demon and Mo Bei merged, leading to the rebirth of a half-human, half-demon monster from the depths of the blood river. SSS级刺客回归, SSS-Class Assassin’s Return, SSS-Level Assassin Returns SSS-Class Assassin Returns, Return of the SSS-Class Assassin