Resolved Looking for novel/manga of mc keeps repeating the dungeon that appeared in the modern world.

Of course theres *spoilers* but only spoils the setting and the very few first chapters.





Hi guys,
I'm looking for a novel/manga with the setting of dungeon(s) appeared in the modern world and it randomly transports people inside. The mc was one of the first to be transported inside the dungeon and when he and the last survivors past through the last gate which takes you back to the modern world, he came back all the way back to the beginning. This keeps on repeating for many years and he met and fought with many people and watched them leave while he stays behind. This ends in the first few chapters as he fulfills some kind of task which allows him to go back to the modern world.

Thank you

 

If the MC's a crazy guy who uses flip-flops as a weapon, does whatever he likes without fear of repercussions and cleared the tutorial tower while roleplaying and also in the nude for entertainment and to keep himself from going insane (not that it helped much), then it's https://mangadex.org/title/48023/the-tutorial-tower-s-advanced-player.

 

@otaku31
This is it, thank you!!!