Heihachi is a young resident of the Edo period setting and becomes a friend to the protagonist, Tokidoki. Despite his bald appearance, which can be misleading, he is actually in his mid-to-late teens, around sixteen to eighteen years old. His most defining trait is his profound ordinariness, as he is portrayed as a completely normal human with no special powers, curses, or particularly striking good looks. In fact, his face has earned him the nickname hyottoko, referring to a comic clown figure from traditional Japanese theater known for its distorted features and large, round eyes.

In terms of personality, Heihachi is generally agreeable, reliable, and hardworking, embodying the spirit of a true child of Edo. He places a high value on his friendships and is the type of person who would do anything for those he cares about. He is usually polite, though he has notable vulnerabilities, particularly when his self-esteem is pricked regarding his appearance, which can send him into dramatic, sparkling fits of depression. He also has a tendency to react very dramatically, or spazz, when he is startled, annoyed, or scared.

Within the story, Heihachi serves as a grounding presence as one of Tokidoki's first and most normal friends in a world filled with supernatural conflict. While other characters may be embroiled in wars between humans and demons or possess strange abilities, Heihachi represents the everyday person trying to live his life. A key relationship for him is with another character named Tsuyukusa. The dynamic between Heihachi and Tsuyukusa is noted as a particularly engaging aspect of the series. Regarding his personal development, he does not possess any notable abilities or powers, which is a central part of his character as the average everyman amongst more extraordinary individuals. Information on any significant character arc or change for Heihachi is not available.