GF lied about her schedule to MC and should be going to the 会長's apartment. (The author did not clearly indicate that it is 会長's apartment, but it should be by the situation.At least it's not the room MC is in.)
MC also went to the 副会長 by himself(in Student Union's classroom).
MC is tied up, but should not be a slave(Just like a play)
He and she still love each other, but also enjoy having sex with other people.
The difference is that GF doesn’t know the MC's situation, but MC know(And he also enjoys her having sex with 会長.).
My English is not very good, I hope you can understand.
Finally, I would like to ask what does VPs mean?(Although this should not affect what I said above)
Their situation only continued with no real change since the previous work. A disappointing conclusion, even if you ignore yet-another-cuck end. The story in this chapter may have been lame, but Densuke's art really is great.
I'm referring to the increasingly popular NTR ending where the protagonist knows that his girlfriend is cheating on him and becomes aroused by the situation. Sometimes the girlfriend knows this and sometimes she doesn't. In this case, the protagonist's girlfriend does not know that her boyfriend knows of her cheating. "Cuck" is short for "cuckold" (in case you were unaware).