Wrong, YJH isn't the only person mentioned to be the "person he loves the most" but it's actually his whole team mates. I'm a huge fan of this novel so I also a lot of reddit and been in discord groups before for this and we all agreed it was his whole team mates.
No, Novel is clear about it was YJH the one to kill him.
"And also consider Kim Dokja relationship with other, their companions is literally also take a part to kill Kim Dokja, they crying, they also suffer, remember how uriel, gilyoung and yoosung crying, are them not included? Kim Dokja that I know is really love their companions and family"
"They cried, screamed or were filled with deep anger. Everyone was coming towards me. My vision gradually diminished and all the characters became the landscape. I saw them and laughed.
「 Incarnation Kim Dokja will be killed by the person he loves most. 」
I had forgotten. All prophecies couldn’t be interpreted literally. In this Star Stream, people were stories."
"But in this case kim dokja himself who say that prophechies couldn't be interpreted literally, that in star stream people is story. He literally tell that the person he love the most is the characters from story he love the most, after seeing all of them, all of them basically kill Kim Dokja and Yoo Joonghyuk as the protagonist who give him the final blow."
I personally think YJH was the final blow but all his companion was also "the person he loves the most"
Up to this point, everyone knows who is the one who is going to Kill KDJ for real.
Ok, just remember that he Loves YJH not as a person (although he cares for him as a friend), when Dokja was being bullied and lived his worst years of his life, it was the story of Ways of Survival that kept him from harmed himself. As Dokja's mother will point out, he loves the YJH of the novel since he was the one where he was leaned on to carry every shit on his life.
KDJ love is honest, fraternal, not romantic. Still, I love the lore around it, its so relatable when you can emphatize with a character of any story and that character helps you deal with some shit... That's what happened to Dokja and that's why this arc is so good.