Announcer Sekiguchi is a human character who appears as a play-by-play announcer specifically during the Scramble for the Throne arc, where he replaces the previous announcer, Yoshigai, for the duration of the competition. He is an original character created for the anime adaptation and does not appear in the original manga source material.

Sekiguchi is characterized by a passionate and hot-tempered personality, which stands in contrast to the gentler demeanor of his predecessor. He often performs the role of a straight man in comedic routines, frequently reacting to and being enraged by the antics of his color commentator partner, Kazuo Nakano. Despite his fiery nature, he is also highly emotional, capable of shedding tears when witnessing the deaths of justice Choujin or moments of reconciliation between rivals. For example, when Nakano became overly distraught and mourned the fallen fighter Warsman as if at a funeral, Sekiguchi reacted by kicking him. Conversely, he showed great excitement and delight when Kinnikuman secured victory against Kinnikuman Super Phoenix.

A notable and recurring visual gag associated with Sekiguchi is his habit of becoming so excited during his broadcast that he climbs onto the announcer's table. This behavior is highlighted in an eyecatch sequence unique to his character, where he stands on the table speaking into his microphone, only for the table to split in two, leaving him embarrassed. This trait serves to alleviate the otherwise serious and intense atmosphere of the story's conflict. His role in the narrative is primarily functional, serving as the energetic voice guiding the audience through the tournament, and as a result, he does not appear in subsequent installments of the series.