Again, this is mere philosophising on my part and entirely speculation, but I want to assume the whole "Young Hunter" bit is a very obvious set up to have Starling be the new "Villain" of a house game, and have Hunter be the classic young stud protagonist.
It's all coming together if you will. Sterling bitching last chapter about how "one more woman to satisfy and I'm gona break," Hunter getting a young body, everyone now knowing about the incest and being really horny around it... much like the Drew and Kevin golden endings were NTR endings that still presented either of them as the protagonists of their story, the Young Hunter bad ending is just gona have him be the protagonist of his own house game, with Sterling now in PRIME "generic white jock dude rival" design too.
Like, I can see it as if it's coming out today. Sterling has too many people to satisfy, doesn't "organize" his time correctly, Young Hunter satisfies them instead, and becomes the new man of the house/big brother/family venture/sexbot- wait the last one doesn't work- anyway he becomes the new patriarch filling the "power vacuum" Sterling cannot fill anymore.
Why is Lucia going along with it you may ask? She of all other character should be far more primed with this sort of storylines?
Don't you remember the end of her storyline last chapter? She got her "Abed from Community" Genre Savy Autism Savant Spectrum fucked out of her via the use of Weed and Incestuous Orgasms. And we do know from a previous spoiler, that Young Hunter is seemingly get everyone even horny than usual with the drugs in the soup now (Which is now a "zany" and "charming" character trait since he's the hero of the story rather than the villain of course), so of course Lucia is now "up" with Hunter's shit.
He is a young man, he is a house game protagonist now, and she likes those, and she likes sex on demand.
Of course she fucks him.