For the folks asking, sadists seek pleasure in inflicting pain or humiliation. Doms/Domination is when a person takes control of your entire life and you lose agency over many decisions, down to the basics of what kind of toothpaste you use.
Typically, sadists have play times/sessions/sex and it doesnt extend outside of those predetermined sessions. This is the relationship that Wookyung originally agreed to with the ML. What a dom does extends into your real life and not just sex.
Why people are telling Wookyung to use his safeword here is because the ML has gone beyond the boundaries of their initial relationship without Wookyungs consent. Its not about the physical/sexual things going on in this chapter.
Omg now that I've think about it. Wookyung may not know that he might prefer a Dom than a sadist. Since he has been in messy relationships without clear boundaries and stuff. And him not having an opportunity to truly test the limits of his desires, maybe a Dom is all he needs.
And the seme might be the perfect partner for him to basically understand the rest of his desires.(‘◉⌓◉’)
This is what the uke wanted. Like I know its not written the best but at the very least the author has made ukes intentions clear from the start. He has said he doesn't like gentle sex, he only enjoys it rough. To the point that he does "rape", drunk sex and power imbalances (his tutor). Even this chapter the author tells us he's enjoying it and even that he wants more, he's not safewording because he wants it like this, not because he is scared or any other reason.
I understand this isn't everyone's cup of tea, I personally read these to spice things up. So I at least understand when I read a "psychological" drama BL what kind of thing I'm signing up for. It's not particularly safe, definitely not sane, but it is consensual.