I've read the raws and you are close to being right. It is sooin imagining different scenarios. Though your right about chihwan waking up and immediately looking for sooin. But he's not frustrated, just scared something bad might've happened to sooin.
YESHHH I was close MMMWHAHAHAHA AH I just realized you spoiled it for me- its oki THAT SOUNDS SO SAD are they oki though
Yeah, they're perfectly fine. I'm pretty sure the next chapter is the final one though which is sad. I didn't see any extras in the raws but maybe, hopefully the author will add so cute little side stories ヾ(❀╹◡╹)ﾉ~
Ahem NOOOoOOoOOO I think it is nunu illusion maybe he woke up and immediately looked around for him for a while and is now frustrated AKC-