I just played all the way through. At first, i was enjoying it because satoshi was a pathetic lil beta who deserved to be cucked, but as time went on, i began to feel bad for the little guy. After i went through the swinging route, the game gives you a choice for satoshi. Basically satoshi just up and leaves that cheating bitch at the resort - he has just had enough betrayal. The game says this is a bad end, but i say its a great ending. The guy just says "fuck you you worthless slut! Fuck you, you shitty betraying family member!" and just leaves and ghosts everyone who betrayed him. Its not a bad end, our pathetic beta took the first step to alpha-ness. And that is not being afraid to walk away - not having obsessive attachments.
I deleted the game afterwords, because i felt that the story couldnt get any better - it had reached a perfect ending for me. I just want to say that i thoroughly enjoyed the game - ive read a lot of NTR, but very rarely do i feel anything for the characters involved - great job