Akasaka is a detective from Tokyo who first met Rika five years before the start of the series in Hinamizawa while he was investigating the abduction of a child during Himatsubashi-hen. Being one of the few to witness Rika's serious side, Rika warned Akasaka about the later death of his pregnantwife and her death five years from that time. While bummed out that the captives of the child got what they wanted from their abduction, Akasaka later learned that his wife was killed from falling down a staircase despite his newborn child surviving. He brushed off the news as nothing serious and thinking his wife's death was a coincidence until he heard of Rika's death five years later. Regretting his ignorance of Rika's warnings, Akasaka took up training in martial arts to clear his mind and imagine a scenario where he could have saved his wife and Rika.
These wishes come true when Hanyuu's time looping results in a scenario in Matsuribayashi-hen where Akasaka heeds Rika's warnings and saves his wife. He returns five years afterward to Hinamizawa to assist Oishi in investigating the yearly town festival murders and to protect Rika from her murderers. Akasaka retains his skills in the martial arts that become a valuable asset in dealing with the men trying to capture and kill Rika.