I don't. It was a joke. Maybe even a little bait
But also, a bit serious; can you NTR yourself?
I suppose if u suffer from schizophrenia TECHNICALLY it would be?
I have seen the following scenarios actually happen:
1. you become a demonic clone of yourself. you can then possess another person and leave your original self clueless. (thanks to magic just being rationalized by non magical beings). then you can cuck him. and he will rationalize it in various ways.
only seen the one example of this happening.
2. create a fake identity and wear a disguise / shapeshift.
use the alternative identity to NTR yourself. (I have seen an MC "whore" out an unaware wife to his shapeshifted clones. I have seen an MC rape his girlfriend under a fake identity. Blackmail the waifu. Or just seduce her).
your wife/girlfriend thinks she is cheating on you, but in fact the other man is you in disguise.
this one is fairly common
I typically drop the game/quest once this self cuckoldry starts happening.