games by
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fits the bill here
in
Gambler's Game you basically play the casino with your girlfriend on the line, lose and she gets fucked, lose too many times and she permanently becomes the other guy's
you do choose your opponents so you can pick which one you'd rather be cucked by
in
Remote Island Survivors you're stranded on an island with your gf and four other guys, you need to gather stuff to eat and build with, and you do that by splitting into pairs (6 people so 3 pairs) to explore
naturally, you can pair your gf with other people so she gets fucked
unfortunately both are MTL, but if you can tolerate that...
another one that comes to mind is
Leane of Legitimate Crown, you're a commander working for a king set on world domination (or something), conquer cities too slowly and your king will turn your female generals into his sex slaves, lose battles and your female generals will be captured by the enemy to be turned into their sex slaves
then there's the Mijiishi stuff, like
Luxoria and
Amor, where you can straight up march to a guy with your girlfriend in tow and go "okay, now you two fuck"