I loved this drama. the story was well put together. I think the ending left some a little confused tho so I just want to clarify. It's a infinite time loop. Ji Hoon dies, causing trauma to little Jae Woo, which sets into motion all the events that inevitably lead to Ji Hoons death. If Jae Woo had not returned to save Ji Hoon, Ji Hoon wouldn't have died because the only reason Ji Hoon knew to go out to save little Jae Woo was because of the actions of older Jae Woo while he was there. Confused yet? lol So at the end in Ji Hoons letter he says "return to me in 15 years, then another 15 years", what he's saying is he'd sacrifice his life forever so he can have the chance to love Jae Woo. A beautiful story.