Ditto

A broken radio creates a strange connection between two students. In 1979, Yoon So-eun studies at Silla University and loves amateur radio. One night, she hears Ji-in, another student at the same university. The strange part is that Ji-in lives in the year 2000. Neither believes the other at first. They arrange to meet beside the university clock tower. Both arrive at the same place, but they still cannot see each other. The different weather around them finally reveals the truth. They are separated by twenty-one years.
So-eun is already falling for Dong-hee, a student returning from military service. She often talks about him with her friend Sun-mi. Ji-in, meanwhile, spends time with Seo Hyeon-ji, who quietly cares for him. As the radio calls continue, So-eun and Ji-in become close friends. Ji-in shares small details that prove he really comes from the future. So-eun eventually accepts their unusual situation and starts sharing her feelings. Then a student protest changes everything when Dong-hee gets injured. So-eun visits him and writes her name on his cast. Ji-in later discovers a connection between Dong-hee, Sun-mi, and his own family.
Ji-in cannot stop thinking about what he has learned about his family. He looks through old photos and finds a university yearbook from 1979. So-eun’s name appears there alongside memories connected to his father. Curious about what happened to her, Ji-in searches for her in 2000. He finally finds her working as an English professor. She is single and seems to have built a peaceful life. Ji-in decides not to approach her or disturb that life. Instead, he hopes to explain everything through their radio connection. But the calls become less frequent, and then they stop completely. Their unusual friendship across twenty-one years comes to an end.