Gonna make the assumption you either know the Sword Art Online characters or you can look em up, as it's a very popular light novel/anime/manga
Currently there's a Part 1 (completed) and a Part 2 (in development). Most of the side characters don't show up till Part 2, though several are referenced in Part 1.
Main Characters:
MC: Kirito (SAO)
FMC: Asuna (SAO)
AC: Inoda (original character)
Side Characters:
Females from SAO with sex content: Lisbeth, Suguha, Shino, Kyouko, and Alice
Other Females: Quinella
Males: Klein, Agil, and Hebishima (original character)
Basically the game follows Kirito and Asuna 2 years after the Aincrad Arc (as far as I know it's very unclear whether the ALfeim Arc happened in this story) when they've been playing this new VRMMORPG, named FOG, and they run into what they assume is a low level player Inoda and then they decide to help him out cuz he's having trouble leveling due to his skills. Being an NTR game you can probably guesss where the games goes from there. It's a very slow burn game, with quite a bit of dialogue and side character content. One of the biggest draws to the game is that all the sex scenes are animated with 3D models, the same 3D models you see during dialogue.
The current development cycle is that the dev drops a content update at the end of every month, and then each week gives a status report of content he's either finished or is working on.
If you like slow burn NTR, where the female doesn't instantly become a slut after being fucked once, I highly recommend playing Part 1. Whether you decide to play Part 2 after that is entirely up to you, just know it's not finished and does kinda start slow cuz it introduces like 4 new characters that all get quite a bit of screentime. So if you're only here for Asuna, and don't care about anyone else, I'd wait longer for more scenes to be made in Part 2.