Hideo Mochiyama is a supporting character in the anime Angel Heart. He is depicted as an adult man of Japanese origin with black eyes and brown hair that reaches his neck. His physical appearance is marked by a heavyset build, and he is typically seen dressed in a suit with a tie.

Mochiyama operates as a member of the yakuza, the Japanese criminal underworld. Within this world, he serves as a subordinate to a powerful figure named Li Chien Dâ. His role in the story, while limited, is significant during a particular turn of events. He is present when his boss, Li Chien Dâ, comes under attack and is shot. In the aftermath of this violent incident, Mochiyama is the person who shows the protagonist, Ryô Saeba, a photograph of a young woman. This woman is Xiang Ying, also known as Glass Heart. By revealing her face, Mochiyama helps Saeba realize that she is the girl who now carries the heart of his beloved late partner, Kaori Makimura.

His personality is initially defined by fear. Upon encountering Glass Heart, whose lethal skills are formidable, Mochiyama is absolutely terrified of her. This fear shapes his early interactions with her. Over time, however, his character experiences a subtle but clear change. By observing both Xiang Ying and her companion, Xin Hong, on multiple occasions, he becomes wiser and more settled, suggesting a growth away from his initial cowardly panic toward a more measured and understanding disposition. In his first encounter with Xiang Ying, he carries a Zastava M57 pistol, a specific detail observed in the anime adaptation. The Japanese voice actor who provides his voice is Naoki Tatsuta.