A poor student at an expensive South Korean academy receives much needed math tutoring (and a place to stay) from the school's security guard. The student later discovers that the security guard is in fact a mathematical genius who defected from North Korea. He had made progress on proving the Riemann Hypothesis, but defected with his son because his government cared only about his work's cryptographic implications. The mathematician put aside his research after his son died while trying to return to North Korea.
The teacher of the student's math class is portrayed negatively. He does not appreciate the student's improved mathematical ability because the teacher is only interested in grades, not in the beauty or truth of mathematics. Moreover, the teacher helps his students cheat in a math competition.
Spoiler Alert: The movie concludes with a "feel good ending" showing the (former) student and security guard meeting again at Mathematisches Forschungsinstitut Oberwolfach years later and discussing math.
Thanks to Zin Li for bringing this work of mathematical fiction to my attention.
