༺Iཽsཽ Tཽhཽaཽtཽ Yཽoཽuཽ?༻

A girl of 23 years and a boy of 25 years met in the streets of Busan "coincidencely" but again meet in the future as enemies. Who is she? And who is he? Is their meeting really a simple coincidences? What type of past does they have? Let's see what fate have decided for them