That is not what NTR means. You're monthly annual post of being incorrect about something never fails.
The term NTR /Netorare come from Japan and it occurs when a character's partner is stolen, and or taken. Whether the partner does so willingly is irrelevant. You can read Japanese Manga, or Korean Manhwa and get examples first hand on the NTR genre. I'll give an example, "Everything's Agreed" is a Korean manhwa that has Netorare, Netori, and Netorase all in the same webtoon. One of the character's girl is tied to a bed after being kidnapped and has sex forced on her. The MC doesn't see it. The woman isn't a willing participant, yet she's being "taken" by another man all the same. That's an example of Netorare. Now, with that said, a cheating partner can be seen as Netorase OR Netorare depending on the dynamics on the relationship. Going back to the manhwa I mentioned, the 2nd MC's has a Netorase fetish that he didn't previously know about, aka he's a cuck. As his girl is being forced to have sex he's actually turned on by it, such as Oliver does when he watches Stephany in this VN. The girl gets off being fucked by strangers while blindfolded, knowing her man is watching it and getting off. Eventually it goes from Netorase into Netorare as she realizes she enjoys it even without her man being present. I type this in an attempt to clarify for those that may read you constant misinformation about what happens in this game.
Stephanie and Oliver are both learning and pushing each other to test the limits of what they enjoy, and what could eventually end up being too much. For those that don't hold down CTRL and actually read their convos, nothing happens without permission. They have talks about pushing the other with the knowledge that the other can put a stop to anything at any time if they are uncomfortable. K4soft has placed situations where Steph didn't know what to do and was waiting for Oliver to stop thing from progressing, but he didn't. Steph was visibly uncomfortable but didn't stop because she thought it was what Oliver wanted, and they talked about it later. Just an example of the fact that they are still learning, as things in that particular situation could have ended badly if Steph allowed herself to go too far thinking it's what Oliver wanted. Likewise that would have meant Steph would have been in an unwanted sexual act thinking it was what Oliver wanted her to do, as her main goal is getting Oliver off via his cuck fetish, while obviously enjoying herself while doing so. Their relationship is 100% Netorase and has never dipped into Netorare at any point. Last, Oliver has given Steph permission to sleep with Arnold even when he's not around, because he wants to come home and catch them in the act. Steph could have had sex with Arnold at any point and yet to do so.
I hope that clears thing up for any newer players that are on the fence about the content within the game. Download and enjoy if you are looking for Netorase/ sharing/swinging/ cuck content. If you are looking for a cheating wife, hardNTR/ Netorare, it's not in this game.
Sorry for the wall of text!