Alright, lets see...
If memory servers i found it only a year or two ago and I do believe I found it here on F95. The artwork was 2D, largely in the form of portrait cards that would be random men and women. The player character was a card like these however you got to customize your MC appearance. In this way at the start of the game you'd see all the other characters up on the surface and could sort of interact with them and what they were doing. I didn't really do that myself since I can't read Japanese. Once you go into the dungeon you would see the cards for most of the adventurers who decided to go down into the dungeon too, and as you went down in floors it would become less and less depending on how cleared the floors previous were. If you were captured by monsters, you'd get a black screen and hentai text. Then you'd wait until some other adventurer reached your level and defeated the monster you were being held captive by. If i remember right you could rescue other adventurers or leave them to their fate if they were a rival of yours, but being unable to read it was usually me being the captive.
I know that my playthrough was as a fem MC, i don't remember if it allowed for male MC.
I know the art style was almost an older anime style, and not a modern style or chibi art style.
I'm fairly certain it wasn't multiplayer, as it didn't require an internet connection. If it had LAN capabilities or if MP was a planned feature i have no idea.
The whole game itself seemed various flavors of RNGs, except ofc where the MC was involved and the fixed "starting town".
Speaking of the starting town, there was no sprite movement in this game. EVERYTHING was menus with background art.
I hope this is helpful, again I know how much of a shot in the dark this is so I do appreciate the time of day.
