Lesson in Murder [Spanish]

Masaya Kakei is a university student, but he attends a school that's not his ideal school. His days are generally gloomy. One day, he receives a letter from serial killer Yamato Haimura, who was convicted for eight murders and received the death penalty. Back when Yamato was committing his murders, he ran a bakery store. At that time, Masaya was a middle school student and a customer at his bakery store. According to the letter, Yamato confessed to committing the murders, but he insists that he did not commit the last murder. Masaya begins to investigate the last murder case involving Yamato.