TV-Series
Description
Helmeppo is a Marine officer who first appears as the spoiled son of the corrupt Marine Captain Morgan. He is introduced in the Shells Town area of the East Blue, where he lives a life of luxury and impunity by exploiting his father's authority and reputation. During this time, he owns a pet wolf named Soro, which he allows to terrorize the local populace. When the bounty hunter Roronoa Zoro kills the wolf to protect a young girl named Rika, a vengeful Helmeppo has Zoro arrested. He then breaks a promise to release Zoro after a month of starvation and instead announces a public execution, an act that draws the ire of the pirate Monkey D. Luffy.

In his initial appearance, Helmeppo's personality is defined by cowardice, arrogance, and a deep-seated sense of entitlement. He is a bully who hides behind his father's power, threatening to have anyone who displeases him killed. He is portrayed as whiny and petulant, running to his father to solve his problems. However, this spoiled facade begins to crack when his own father strikes him down for giving orders. A pivotal moment in his development occurs when Morgan, after being arrested, takes Helmeppo hostage during an escape. Realizing his father is a brutal criminal who cares nothing for him, Helmeppo severs their relationship and vows to become a stronger, better Marine in order to one day capture his father and bring him to justice.

Following his father's downfall, Helmeppo is reduced to a chore boy at the Marine base, a humbling experience that forces him to work alongside a peer named Koby. After the incident with his father, Vice Admiral Monkey D. Garp takes both young men to Marine Headquarters for training. This marks the beginning of Helmeppo's genuine transformation. He matures considerably, shedding his lazy and entitled nature to embrace rigorous training. His primary motivation becomes personal redemption and the pursuit of genuine justice, a stark contrast to his earlier life of corruption. He is driven to prove his own worth, separate from his father's infamous legacy, and to uphold the principles of the Marines he once disgraced.

In the overall story, Helmeppo transitions from a minor antagonist to a supporting ally. He is most often seen alongside his best friend and rival, Koby. Their relationship is central to his character; they begin as reluctant colleagues but grow into close friends and trusted partners who constantly push each other to improve. Garp serves as their stern but effective mentor. His relationship with Luffy and Zoro is complicated; they initially despise him, and even after his reformation, they struggle to remember his name, leading to comedic moments of dismay for Helmeppo. He also shares a connection with the girl Rika, who eventually forgives him and becomes a friend. As a member of the secret Marine unit SWORD, his role becomes more active in the later stages of the story, participating in high-stakes missions such as the attempt to capture Boa Hancock and the raid on Hachinosu to rescue Koby from the Blackbeard Pirates.

Helmeppo's development is one of the most significant transformations in the series. Physically, he goes from a skinny, lanky youth with a distinctive mushroom-shaped blonde haircut to a much more muscular and capable officer, with his hair grown out into a ponytail. Mentally, he evolves from a selfish coward into a brave and levelheaded Marine. He reflects on his past with shame, referring to his former self as a bratty son who lived off his father's status. By the time he is promoted to the rank of Lieutenant Commander, he has become a relatively calm and formal individual, often acting as a voice of reason compared to the more hot-headed Koby.

In terms of notable abilities, Helmeppo is a skilled swordsman who fights with two curved kukri knives. After years of intense training under Garp, he has gained considerable physical prowess, including the ability to jump great heights and defend against attacks that would have defeated him earlier. He has also learned at least one of the Rokushiki techniques, specifically Soru, which allows him to move at explosive speeds. Furthermore, Helmeppo has begun training in Haki. He possesses some proficiency in Kenbunshoku (Observation) Haki, which allows him to sense the presence of others, though he admits his skill is not as refined as Koby's. He is also capable of using Busoshoku (Armament) Haki, which grants him enhanced offensive and defensive power, allowing him to clad his weapons and body in an invisible armor. While not among the strongest fighters in the series, his growth from a complete non-combatant to a competent officer in an elite Marine unit demonstrates his dedication and newfound strength.