at chapter 38, the MC didn't know why Woori was doing it. He didn't directly said No. But dry humping without consent is S'Ad. And if you think he consents it because he raised his hips, Nope. It's not a consent. Did you know assault and rape victims feel pleasure while they are assaulted? That's the hard fact that they don't want to accept. That's why they feel disgusted with themselves. And in here, they depicted it. Woori assaulted him, while MC naivety didn't know what it is. Worst Woori uses the reason of them being friends to his advantage, he's been touchy since the theater scene. He uses Mc's sensitivity and naivety to his advantage. He only stops when the Mc said No at chapter 39. Just because he likes MC, he was exempt from what he did.
He reciprocated the action. "Just because he likes it doesn't mean he consented" in any other case maybe that would apply but in this context it just doesn't dude. Adults can reciprocate and consent without verbally saying anything if they're both sober and capable of understanding what's happening and what they're consenting to. MC isn't stupid, he's just an airhead. He knows what sex is, he knows what woori is doing, and he is actively participating in and enjoying it. People like you are why real SA doesn't get taken as seriously as it should, especially with men.
I love your jump to conclusions about my life experiences, but unfortunately for you I just know how to understand nuance and adult dynamics better than you seem to. You're literally disregarding MC's ability to make his own choices just to misuse the term SA where it doesn't belong. Since we're making assumptions though, I'm going to assume that you are HEAVILY projecting and don't actually have a concept of someone making a choice you wouldn't make.
If your friend dry humps you and you hate it, you would more than likely react very differently than MC and that's fine. But that's not how he reacted and you just need to accept that this character doesn't feel the same way about the situation as you do. Chill out, go outside for a while. You're getting yourself this worked up over an assault that didn't happen to a character that, first of all isn't real, and second did not have negative feelings about what you clearly have big feelings about.
It's you, who's been making assumption about me first eheheh. I go for a walk if that's what you want to know. It's the lack of consent before the act regardless what's the reaction it's an assault. You can call it nuance, I call it missing the point. It's okay, not everyone built for empathy. Take care, mwahh

Guys WOORI didn't "assault" him id agree with y'all if MC literally said the words "no" or "stop" but bro raised his hips like y'all dtm