Responses

Spoiler
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Juwon has sun allergy (only his family knew this) and forgot to pack his medicine for the trip because he was excited to have fun with Siwoo. Unfortunately, Siwoo confessed to Juwon while he was really sick and out of it. This is when Juwon says 'disgusting' referring to how sick he felt. He didn't even know that Siwoo was next to him. I believe he later wakes up at the hospital, and Siwoo leaves the town after graduation for the next 13 years without learning the truth.
Someone spoil me and tell me what actually happened to that field trip