I've got to be honest, I'm bewildered as to why the reviews are so positive. This is without a doubt the most tedious, time-wasting ero-game I've ever played in my life, if you can even call it an ero-game at all. The ratio of "gameplay" to h-scenes is even worse than Fall of Ship, another egregiously bad game with a lot of similarities to this one- it takes multiple hours to get the first h-scene. The first.
The combat is insanely tedious, with individual battles being very easy but an absurd number of them forced upon the player at all times. The player is CONSTANTLY forced to fight meaningless battles against annoying foes that give you nothing for beating them. The game advertises its' lack of a levelling system as a positive, but what it fails to understand is that removing XP from the game and having a system where enemies give you nothing (no gold, no XP, no items- nothing) only makes every single counter nails-on-a-chalkboard excruciating. For some reason, the enemies are extremely aggressive as well, constantly following you through the thin corridors that comprise this game's dungeons and forcing you to fight them long after you started just running past everything. Your time is constantly wasted, and for nothing. The advertisement is correct, there is no grinding in this game- unlike grinding, where you fight a bunch of enemies and gain levels, gold, items and equipment... you fight a bunch of enemies and gain nothing. That's not a positive feature, it's just terrible game design.
The story is very good, but the game is simply terrible- nearly unplayable, to be honest. Combined with the h-scenes of incredibly poor quality (they come out of nowhere, their situations are contrived and meaningless, and the art is mediocre at best), my rating of Ouroboros as an Adult Game can't really be anything above "terrible".
If you are looking for a good ero-game, don't play this- even the people that like this game say that much- but even if you're just looking for a good game, this isn't it either. Don't even download it thinking, "oh, I've got the RPGM cheat engine, I'll just use that to quickly get through", because it doesn't work on this game. There is simply no reason to pick this game up, unless you recently got a lobotomy that makes you enjoy terrible RPG maker combat or a fetish for watching poorly drawn vanilla h-scenes.
Addendum: I don't really take myself seriously enough to bother posting reviews about bad ero-games, things like bad gameplay or terrible pacing simply come with the territory and I've long come to accept that. This game, though... it's rancidness pissed me off so much that I just had to review it. Sorry if I sound ridiculous and melodramatic, but this POS game just wasted almost 6 hours of my life and I got absolutely nothing out of it whatsoever.