Satsujin Hensachi 70

Miyahara Keisuke oversleeps on the day of his entrance exam for Tokyo University. To postpone the exam starting time, Keisuke sends an email to the school warning of a bomb. His plan works and he is able to delay the exam for an hour. 3 months later, the results are out, Keisuke is overjoyed to see that he had passed. On the day of his entrance ceremony, a man named Tanaka Hiroshi appears in front of Keisuke and threatens him about what he did on the exam day. Hiroshi starts following Keisuke around, demanding money in return for his silence over the matter. Keisuke, who had thought life would be all rosy at Tokyo University, is now overcome with fear, and has to even resort to questionable methods in getting the money to pay Hiroshi. As Hiroshi's demands become bigger and bigger, Keisuke becomes desperate and vows to end it once and for all.
~~ Adapted from the short story “Juken Jigoku” published in the short story collection novel “Irebun Satsujin Jiken” by Kyotaro Nishimura.