He could have but he was trying to get wookyung to understand the difference between assault and actual bdsm. But he had to end it in the end because wookyung wouldn’t. I’ve seen and read other actual bdsm scenes where doms will do something similar to subs who don’t understand or won’t understand boundaries. Some just want to ride the high for as long as they want and some get scared that if the safe word they won’t get back to that space. I think wookyung truly does not understand bdsm play vs being beat up and is unwilling at this time to actually even look at the difference. We don’t know much from his home life so maybe something in his home life made it so he feels he needs to be punished and it’s moved into being punished during sex.
If he wanted to stop because he felt uncomfortable with hurting wookyung, then couldn't he have said the safe word himself? Or is the dom supposed to keep on going until the sub says no?