That Dragon: Destroyer

After years of being together, not just as a couple, but as friends, Alexis and Hoseok (Wonho) part ways due to her will. They both refuse to accept it, but no one does anything to fix the situation until he gets a call from a friend. Hoseok drops his phone and rushes outside on the streets of Seoul, running as fast as he can to the hospital, one think in his mind.
Alexis was in the chemotherapy section.
And she wasn't a visitor there.