P.S. Main lead starts his path to OPness from ch.56
At first you get OP MC (I love OP), after that in whole 25 volumes MC developed 2-3 new moves and that's all. That was all his improvement. By the end most of his friends caught up to him in strength, some even surpassed him and at the end of the novel it's difficult even call him MC (Nina took that place I guess). There were countless cities but only 2 were explored and only 2-3 others were mentioned. World exploration really sucked in this one. There were several other disappointing factors but It had been long time since I read this so.