He does try to rape the other girls as well, but Liz is the only one who has the unfortunate luck of letting her guard down with him. She wants to see the best in him(there is no good in his soul) so she doesn't really see him for the piece of shit he is. Other LIs either are already willing to have sex with him(Ellie, Zoe, etc) or will straight up put him in his place(Jess, Nicole, etc.). MC basically rapes the only person who actually trust him, embodying why he is just straight up scum(Guy makes Rudeus from MT look like a great guy).
I will say that to be fair, if the coward wasn't in a grounhog day, he would never have the balls to pull of any of this shit.
i've played multiple porn games, and i do have to say this MC is the biggest loser of them all, which is a very low bar, because much of these other MCs don't have much going for them, lol!