Once Again - Season 1 Episode 1 Hello?

A troubled Jae Woo begins having nightmares again and finds himself recalling a life-altering accident from many years ago. Although he was successfully able to escape the disaster that stills haunts him till today, his savoir, Ji Hoon, wasn't that lucky, meeting his end there and then. On this day, Jae Woo decides to return to Room 303 at the Hanmaeum Dormitory where Ji Hoon previously lived. Feeling like he still has a lot to say to Ji Hoon, Jae Woo picks up the telephone in the room only to hear what sounds like Ji Hoon's voice coming out from the other side of the line.