The jocks are at the party because DPC needed some opponents to give the MC something to chew on!! Nothing more, nothing less!
And about Chad and Sage, it shows much about Sage and not very good things.
Seriously why did Sage choose Chad, he never was smart or very kind or gave her any sex and she is a sex freak !!
She choose him for the muscles, she loved his figure that's all and Chad took that oppotunity to hide his true relation.
So we have a girl, Sage who is mostly interested by the figure of her lovers and for the MC it's the same, he's handsome and so he became her fuckbuddy.
She is not really interested in the MC and he totally understands it, he told her he wanted more but she didn't seem to really get it.
Even when they are closer during the HOT's party she seems mostly annoyed by Chad's presence and uses the MC once again to make him leave.
So for me Sage is just a superficial girl who needs a good fuck, who fantasize on muscular men who will fuck her brains out and who hates to be rejected as a spoiled child. She wants Chad because she has decided so and she won't abandon that idea easily.
She is the female version of most MC in our games !!
Sage, at first, is the cliché popular girl of all American juvenile movies and TV series: the Capitan of the cheerleaders team that is girlfriend with the quarterback of the football team, the queen and the king of the prom ball... We have seen it a thousand of times. Or, in terms of this game, the president of the sorority of the popular, party girls that is the girlfriend of the president of the frat of the popular athletes. The dev makes the athletes utterly stupid and abusive with other students that are not athletes, and the popular girls, superficial and slutty: that's another cliché of that kind of movies.
But at least, it seems that there is character development and narrative arc in this game. Sage was a superficial girl two years ago, when she started dating with Chad, but now she´s more mature, and that's why she bonds and gets attracted by another kind of guy not as superficial as Chad. Someone way more caring, even if she still likes guys with "big ego, big mouth and big cock". Nothing wrong with that preference: she likes manly men, that's all. It´s obvious that Sage is really interested in the MC. As Sarah says, she doesn´t treat him like a "side bitch".
It´s just that now she feels humiliated. As she says, she gave all to Chad, a guy that obviously doesn´t deserve that kind of devotion from her, and so she feels stupid. Like having thrown away two years of her youth with that guy. I think that the MC should feel the same way about Maya and Josy, only at a lower level since he hasn´t been in a relationship with them for years.
Being annoyed by Chad´s presence in the party is just natural. Nobody wants to see their ex around after a bad break up. It´s just a matter of time that Sage forgets about Chad and the MC gets Sage, since she's not a drama queen or a narcissistic person obsessed with her own problems, like Maya, and she can be a loyal person, since (as far as we know) she only starts cheating Chad after she knows for sure that she has been cheated by him, and because of the complete lack of interest of Chad about her.
I´m liking the character development of Sage so far, even being a cliché character. I was annoyed by her being so eager to help Maya (I can´t stand Maya the lesbian SJW, I admit. That´s a postmodern cliché that I really hate and despise) but after reading a post by another user, I have changed my mind and I think that makes sense.
Sage is starting to be a better and more responsible person, and the MC´s influence (if the MC is into his path) has something to do with that, since Sage has seen that she has attracted a guy that actually cares about her, and not only uses her to look good. She has also realized that letting Quinn have the reins of the sorority was a huge mistake and now is trying to fix things. Maya asked her not to have Quinn as a mother, she didn't pay much attention, and now that she left the sorority, Sage thinks that she has some kind of debt with her. That´s a good thing, even if I think that Sage having a plan for getting Maya thousands of dollars for the tuition is to take things way too far. One thing is to convince Maya to return to the sorority by being kind and caring with her, unlike Quinn, and another different thing to be the "deux ex machina" that solve her problems. It´s hard enough to believe when it´s the MC who does that kind of things (coming out with a magical plan to solve other´s problems), and he´s the MC, "Main Character", the one who is expected to do the things in the game.