Not to get all philosophical or anything, but I've always considered cuckolding and NTR as two different things. I mean, yes, they can frequently overlap, but I feel like a cuck can be a thing, but not be considered "stolen" or "lost" in regards to their partner. I personally am not a fan of any relationship that is basically losing your partner and having them stolen, but cuckolding, when done properly can be very hot, and doesn't necessarily have to make the cuck feel any less loved or desired by their partner. This distinction I feel is important. One of my favorite types of play (and I've seen a few examples of this, its always really hot) is when the partner goes out and "Cheats" or cucks him, but then always gives him a chance to "win" her back. There is one doujin that is really well done, where she always makes sure her partner, the cuck, is always being taken care of/active/still involved, and while she threatens many things (only after warning him she will say such things) she still always lets him win her back. In the end, the relationship is one where everyone is on equal terms with complete understanding and expectations of each other. They love each other, but have an extreme kink/fetish they follow, but it winds up enriching the relationship as its consensual on all sides. (seriously one of my favorite/best doujins I've read)