I don't see why it wouldn't be approved on Steam. The characters all look like adults, there doesn't seem to be a highschool (or lower) setting. And you sound like you'd aim for the Adult Only tag, since you wouldn't want to censor it.
Those are things that get games into issues. Underage characters [A Hand in the Darkness], school settings, or trying to make an AO game into an "all ages" version and having various issues in the transition. The last one I remember hearing about was the latter. Manga Gamer reworked one of their games to be "all ages" and accidentally left in some AO images in the game files and it was banned. MG claimed there was nothing wrong about it, but eventually admitted the accident and fixed it and Valve let the game back on. Too lazy to google the name of the game, it was a straight one so it's not in my library easy to check :P The only issue from Valve in that instance was their poor communication of the issue. An issue that you'd not have since you said you wouldn't want to change anything.
The developer of "Uncle Neighbor" said he tried to get it listed without the AO tag which is why the main AO content wasn't available at launch, but failed to get listed without AO tagged. After playing the game, I can imagine why as the non-nude images are still pretty spicy, bulges for days. But the game is allowed with the AO tag.
"No Thank You" is allowed and that has dubious consent, outright rape, torture, murder and other disturbing stuff that I wish I could purge from my memory. "Man Wreck" is allowed and the themes/art are very fetishy and let's say destructive of particular orifices and body parts.
I really can't imagine your game wouldn't be allowed with the AO rating.