Alright, so the chapter starts off, kinda jumping ahead - MC and his party is now back at the school, and we open up with Lucas arguing with Venus about the merits and demerits of polygyny.
(Don't confuse "polygyny" with "polygamy" - it's actually a subset that falls under "polygamy". "Polygyny" specifically refers to polycules with a sole male and multiple females.)
Venus, of course, argues that it's his right, and even raison d'être, to take multiple wives and have them all bear his children.
Lucas is against it for ethical and moral reasons. He's an old man, after all, why would she want to bear his child? And also, the typical strife that occurs in polygynous polycules - the politics, the intrigue, the backstabbing, and the blood letting.
In the meantime, Aria is prying the important details out of Krusha. She practically dies of embarrassment when Aria figures out that Krusha actually does like Lucas enough that she would not mind abiding by her culture's law.
And then we have the stereotypical trope where Krusha asks Aria how she feels about it, answers that she doesn't mind at all, and then Krusha goes on thinking she said "No".... Only to suddenly have a hilarious freakout when she realizes Aria actually said "Yes".
Aria then continues her offensive by telling Krusha that she is more than just "Acceptable" in her eyes, but also cute as all hell (low key implication that Aria would love to fuck Krusha's brains out, too).
Krusha then hits back with the same argument Lucas had: Aren't these kinds of families like living in a shark tank?
Aria: It's an earned stereotype alright, but she comes from one of the better ones - all three wives her father married are good friends with each other, and her half-siblings are all very loving and supportive of each other. Quid pro quo, however: Aria WILL be gatekeeping this polycule.
With this, Aria begins to plot and scheme. It's obvious that Lucas isn't going to willingly go for it, so the matter needs to be forced. Her plan? Get Lucas absolutely rip-snorting drunk with some damn fine booze, then use the classic "Let me go get cleaned up first before we have fun~" excuse... And then along comes Krusha.