The story goes like this- (probably a KR novel) the MC is a lvl 99 OP in his world. After killing the final threat, the system or god ask him whether to remain in this world as the ruler or continue to the next path. He choses to leave the world and see whats next. The MC gets shock, he finds out that even a passerby is lvl 200 or above. He is the weakest in the world. He then trains with a guy from another world and story goes on like that.