The character of Gyoshin's father is known only through a single, pivotal incident from Gyoshin Ayukawa's childhood that explains his son's permanent injury and subsequent estrangement from the family. When Gyoshin was a child, he accompanied his father on a fishing trip down by the bay. That night, his father grew extremely upset over his inability to catch any fish. He began drinking and stubbornly insisted that he would catch a fish that day. As young Gyoshin decided he wanted to go home and started walking away, his father, in a moment of aggressive and reckless frustration, flung his fishing rod backwards. The hook caught Gyoshin directly in his right eye, causing him to lose it. Following this traumatic accident, Gyoshin made the decision to leave home at an early age. His stated reasons were to prevent both his father and mother from worrying about his resulting blindness and to spare his father from the painful reminder of the incident. There are no other details provided about Gyoshin's father, including his background, personality beyond this event, subsequent role in the story, relationships with other characters, any personal development, or notable abilities.