I wonder why he doesn't just call himself and tell himself about it or something... though it's possible with the time thing that his past self doesn't meet jae-ha without future self's interference, they ARE talking about past self right now after all... maybe them talking about him inspires jae-ha to talk to save him?
well first he wouldn't believe and second if he say about the accident to jae-ha every single thing will change
have you ever watched "Nine: Nine Time Travels" we when watch this drama no matter how many time he goes to past and to correct his mistakes every single time something will change well but the end is sad but its good drama
so this is what i'm saying i will change not one but the whole life he lived until now (thats what i think)
if he changes the past and tells JAE HAN THAT scene about accident when gonna happen everything will change