Miscommunication

I don’t remember what happened in the chapter where they showed a small snippet of the confession since it was so many chapters ago. But given that they showed how tired Juwon was prior to the trip, he most likely was half asleep and didn’t hear/understand was Siu was saying, then responded with sleepy mumbling. And Siu has very dramatic responses, so he prob took whatever was said as a rejection, freaked out, then suddenly told his mom he wanted to go to hs in Seoul.