
did they fuck before?

Spoiler
Nope. At first, yuder's narration makes you think they were strangers but the more you read the novel, the more it's explained by yuder that he and kishiar were literally sex buddies in their first timeline. And unknown to yuder, kishiar actually loved yuder in the first lifetime but didn't try to further their relationship because he was injured by the red stone and was destined to die

Spoiler
Actually, in the previous lifetime, kishiar is the one that got hurt by the red stone instead of yuder!! Remember that in the previous lifetime, yuder never followed them to retrieve the red stone. So now that he went along in the present timeline, he was the one that got hurt. The explanation to kishiar's injury is that apparently, every royal family member have a sort of power or vessel in them that must remain untouched or something. I don't know how to explain it but when the red stone hit kishiar in the previous lifetime like it did to yuder in this present lifetime, it shattered his vessel which really injured and impacted his lifespan causing him to slowly fade away
literally snickered when the he said "New Yorkers are so nice"