Heppokomaru, also known as Gasser in some versions, is a central character in the story. He is a quiet, sensible, and easily embarrassed teenage boy who often serves as a voice of reason amidst the chaotic nonsense of the main group. Physically, he is recognized by his long, spiked-up white hair, golden-yellow eyes, and a black shirt adorned with a skull and crossbones on the back. His Japanese name reflects his role, as "heppoko" means "untrained" or "bungling," while "maru" is a traditional suffix for a warrior's name.

He was born and raised in Puppuu City, where he witnessed the tyranny of the Hair Hunters firsthand. To defend his home, he began training in a unique and unorthodox martial art known as Onara Shinken, or the True Fart Fist. Before joining the main rebellion, he was an outcast searching for a powerful ally. His initial motivation was to find Bo-bobo to help liberate his hometown from Gunkan, a powerful enemy from his past. However, his path becomes intertwined with the group when he repeatedly steps in to rescue Beauty, for whom he quickly develops deep feelings. Despite his powerful abilities, Heppokomaru is often relegated to the sidelines during major conflicts, reacting with shock, horror, or exasperation at the bizarre antics of his teammates.

His role in the story is that of the comparatively normal heart of the group, similar to Beauty. He is a loyal supporter of Bo-bobo, whom he respectfully calls "Mr. Bo-bobo," and he trains diligently to improve his skills. His key relationships are central to his identity. He harbors a significant, unspoken romantic love for Beauty, who affectionately nicknames him "He-kun" or "Gas-Can." This infatuation makes him protective of her and prone to blushing and awkwardness in her presence. Conversely, his relationship with the volatile Don Patch is one of mutual annoyance, with Don Patch often attacking him, leading Heppokomaru to retaliate with a punch. He forms a much friendlier bond with Tokoro Tennosuke, showing genuine concern for the tokoroten warrior and even developing tag-team moves with him.

Heppokomaru undergoes notable development, particularly regarding his fighting prowess and personal loyalty. He initially struggles with his lack of confidence and control over his abilities, which are regulated by a special collar around his neck. If this collar is removed, he regresses into a powerful, unstable, and infantile state referred to as Baby Heppokomaru. Later, after a period of separation and intense training, he masters his art, achieving a form known as Kakusei Onara Shinken, or Awakened True Fart Fist. During the story, he is manipulated into temporarily becoming the commander of the Neo-A Block for the Neo Maruhage Empire after his younger sister, Pokomi, is taken. He takes power-enhancing pills that corrupt him into a demonic, amnesiac form, but he is ultimately redeemed by Bo-bobo and rejoins the team.

Heppokomaru's notable abilities are centered entirely on his Onara Shinken. He can produce flatulence powerful enough to blast opponents, create concussive explosions, and even propel himself through the air to fly. A distinctive feature of his attack patterns is that his techniques are named after months of the calendar, such as "October," where he creates and throws bomb-like orbs of gas, or "November," which summons a massive dragon-shaped cloud to engulf the enemy. His Awakened form grants him even greater power, manifested in a demonic appearance with longer hair, horns, claws, and a tail, marking a significant and fearsome evolution of his natural abilities.