@Lux dude, Suwon killing Il is the literal premise of the manga. As much as it'd be cool if people could be surprised about it as surely people were when reading it for the first time in Japan... it's the hook of the story. Ultimately, provoking interest in the manga itself is more valuable than using the element of surprise for one single chapter. If they leave out the murder and try to pose the manga as a straight forward love-triangle love-story, tons of people will bypass it because they have no interest in that story. Moreover, people looking for a straight forward love story will dig into it without realizing what they're getting into and are likely to drop it by the end of chapter 1.
@zanzwi I found Yona really late and binge-read all of the released chapters in a few days (up to chapter 150 or so i think)
I immediately fell in love and it also left me as an emotional mess. Haha
I am rereading yona in my native tongue, but they are currently on hiatus with releasing the next manga... sigh.