The story is so vivid, it must have been based on eyewitnesses, and then turned into a story.
I myself can testify to the realism. That Korea of 1986-1987 was so similar to the one I saw in Summer 1988 when I went there for the first time ( demonstrations at Ewha, tear gases in the street, German TV crew filming, signs in a Jamsil church asking the military not to gas the building, demonstrators meters away from the Catholic cathedral just in case the police would charge, ...).
The short segment with music only, showing the girl thinking about writing the illegal work, is nothing short of amazing.
A detail towards the end of the episode struck me. Among the students preparing for a demonstration a female student with a bandana in the background is writing a sign. She reappears holding her sign during the fight when the police throws tear gas. I asked myself: is that a cameo of the writer of the KBS episode?