The Lost City of Alien Beasts

Gao Yang is an orphan who, at the age of six, crossed over to a "parallel world" and has since lived in a warm family of five. At the age of eighteen, Gao Yang accidentally discovers the truth of the world: it is not a parallel world at all, but a mysterious realm where all the relatives and friends around are terrifying "beasts"! (Source: Webnovel)

An orphan, Gao Yang transmigrated to a parallel world at the age of six, and was given the gift of a loving family of five. However, with the coming of his eighteenth birthday, Gao Yang found out by chance that this is no parallel world. Unfortunately, he now finds himself in a strange domain where his family and friends can all be terrifying monsters! He was almost killed when he realized the truth, and he would have been dead if not for the system and talent he acquired at the last moment. Gao Yangs luck had suddenly changed for the better and after looking over his stats, he comes to realize that the longer he lives, the stronger he will become! Let the journey to becoming stronger begin! Now commenced the battle royale of a lamb among wolves… Original Novel Official English