The paintings [spoilers]
I just finished watching this movie and there's one thing I don't understand. At the start, Ryu sends his story to the radio station along with a painting of him and his sister by the river when they were young. Later on when Park goes to the station (after Ryu had called in to say his sister was dead), the woman there gives him the painting and there's a second one of Ryu burying his sister with Yoo-sun in the water.
So who made those pictures and how did a painting of Park's dead daughter get sent to the radio station?