Horumon Yaki is the head of the Horumon Clan, a group of Choujin from Horumon City on Planet Kinniku. His name is derived from horumonyaki, a type of Japanese grilled offal dish. Long ago, the Horumon Clan was a powerful faction, even greater than the ruling Kinniku Clan, but a war led to its downfall at the hands of the Kinniku Clan. As a result of this conflict, Horumon Yaki personally challenged and lost to Mayumi Kinniku, the former prince, countless times. The war also resulted in the death of his wife, Harami, at the hands of the Kinniku Clan.

Driven by this history of defeat and personal loss, Horumon Yaki seeks revenge against the Kinniku Clan. To achieve this, he initially sends his own daughter, Bibimba, on a mission to assassinate the current prince, Kinnikuman. When this plan fails, he enlists the aid of Shishkeba Boo from the Barbecue Clan, promising him Bibimba's hand in marriage as a reward for eliminating Kinnikuman.

Despite his initial bitterness and role as a villain, Horumon Yaki undergoes a significant change over the course of the story. After his daughter Bibimba falls in love with and eventually marries Kinnikuman, he reconciles with the Kinniku Clan. In his earlier appearances as a destitute and vengeful rival, he is depicted with a shaved head. However, after his reconciliation and his daughter's marriage, he is shown wearing a mask, similar to most other inhabitants of Planet Kinniku, and becomes a respected elder.

In the sequel series Kinnikuman Nisei, Horumon Yaki appears as one of the four great elders of Planet Kinniku's Choujin Council, indicating his elevated status and that the old feud has long since been resolved. Information on his specific combat abilities is sparse, though his designated Choujin Kyodo power level is 50,000. His primary role in the original narrative is as a catalyst for conflict, the patriarch of a fallen house whose desire for revenge drives the plot forward, ultimately leading to an alliance through marriage.