So true the main couple side stories shouldve focused more on the fluff rather than opening up problems that were already dealt with for the sake of being more realistic… the side couple dynamic is a lot more interesting looking back or maybe I’m just a sucker for the top turned bottom trope lol. I just personally cannot see how siwoo could ever go past casual sex to lovers with Do hyeok realistically without some sort of redemption time skip and chasing arc on Do hyeok’s end. While I hate to have bad endings in yaois, Do hyeok being thrown away by Siwoo at the end (similar to what he did to Suha) kinda fulfills the whole karma’s gonna come back at you plot line the author was hinting at when they said Do hyeok would be punished dutifully in the authors note. If I’m missing anything deeper I’d love to know!
I can now see why the author ended the story the way they did with the whole karma thing and i would like to kinda expand on that. it makes sense but I think more development or chapters before closing they're story would be more beneficial maybe storywise as it would raise the emotional stakes of dohyeok if he did become a better person but because of his past actions it would haunt him aka not ending up with his lover and his lover unable to see the good change in him. As a reader personally if i get invested in a couple i would usually like if they ended up together or itd be a waste of time ( aka. The backlash ). But if the authors main theme was to point out you reap what you sow and probably didn't want to get backlash maybe being able to punish him for what hes done and make a bittersweet ending, or and open ended ending. For example forgetting they're past and introducing themselves to each other again for a fresh start they're future undetermined for the reader to speculate. Which would still be pretty sad for the reader but still has the slim chance of being together than the original endjng. I honestly don't think the author would put this much effort into the story and try to hammer home a theme to us readers, so ill just hope for good enough writing and a good satisfying ending for myself personally.
To add on I can assume that the author didn't expect everyone to fall in love with Dohyeok so much after the main story because back then we all hated him haha and even the author didn't expect us to forgive him in the author's note.. which could be another reason for the ending we got... with his rise in popularity I also hope the author can give him a more fleshed out ending like you suggested as well, it would really tie the whole story together. I mean if the two dudes from Sadistic Beauty ended up together in the end there's definitely a way to bring Siwoo and Dohyeok together eventually lol but for now we just have to wait and see.
Firstly, we already got tons of chapters for the main couple and now that there's MORE chapters with stupid miscommunication people are tired of it. Then, While the side couple was toxic, it was interesting to see what was going to happen and dohyeok and what his possible character redemption ( hopefully a good one where it takes time for him to truly change and show his struggles as he becomes a better person, appologize and get consequences that would teach him a good lesson aka.not trying to manipulate ur lover to do it with you) would be. Thirdly, we got left on a cliff hanger and then resuming to the main couples daily life with the same problems that were solved from before so ofc this felt like a drag since there was so much interesting drama in the side couple. finally if you think about it, the interaction of suha and dohyeok would be interesting to see if we see dohyeok change. No suha doesn't have to forgive dohyeok for what he's done or stick around to see if he became a better person, but just know that he became a better person and won't hurt anyone else aka the seme since suha and him are friends. if you disagree with me on any of my points lets have a civil discussion below!