The story starts with MC entering a dungeon (just for sake of it: dungeon = place filled with monsters and bosses. When defeated MC is strengthen gets items, skills and spells.). Before story hits chapter 10 though, the earth experiences the change and monsters and such start appearing in real world, at the same time people with super powers start appear as well. Unlike most idiotic MCs that would go out to save the world, our MC decides to stay at home and level up in dungeon as unlike in real world, in dungeon he is immortal (even if he dies he just needs to wait a week for re-spawn). In any case for few years MC is just doing his missions and interacts with people from other worlds in dungeons with absolute zero care about what happens on earth. At this point the number of potential heroines is 3 so it's not too bad.
Still suddenly the story takes shift. For absolutely no reason what so ever, MC suddenly becomes a hero... not by doing anything mind you but rather by ignoring the world and doing his levelling up. He didn't save anyone, nor did he defeat the big bad boss, no he simply got few achievements and grinned his stats but suddenly the author decided to label him as a "HERO". Soon after, yet again author changes MC and MC suddenly has misgivings about helping people and saving them from dying... worst part of all without any warning before I even noticed MC became a generic dense protagonist that wants to save the world... sigh, where did MC that had zero care about world's problems and just wanted to earn money went to? Putting those two together it's really like two different MCs and two different stories all together.