When twelve year old Sora gets sick, Daesung is there for her, as a favour for her.  Soon, her visits at least once a week.  It's hard to see this once bubbly, energetic girl decline as the disease that claimed her vision starts to claim more and more of her.  Yet throughout the whole process, Sora is all positivity, almost like a ray of sunshine, or better yet, Daesung's little patch of blue sky.