As a fan of NTR, this was really dumb. It's just swapping the whole time and then, "oh it wasn't!" as the finale... but seriously, there was no build up, no stealing, nothing but a swapping fetish the entire time. *rolls eyes*
It seems like the author didn't know how to end his story, so he did the same thing a lot of shitty NTS authors do... SUPRISE MOFO! NTR twist out of nowhere that makes absolutely zero sense... Just why dude? Could've just had a normal aah swinging doujin, we don't get many of those.
What the fuck? Just call the police and get everyone's asses on jail easy as that but that aside serves him right for having such a hot gf and still get roped with such a downgrade.