Dr. Gunma, also known simply as Gunma, is a character from the comedic adventure series that began with Nangoku Shonen Papuwa-kun and continued in its sequel, Papuwa. He is a recurring figure who serves as a scientist affiliated with the organization known as Gamma, later called Magic. Born on May 12th, he is the same age as his rival, Shintaro. Physically, he is depicted as a young man with blonde or yellow hair that reaches his chest and blue eyes.

Gunma’s personality is a striking blend of childishness and deep-seated resentment. He carries himself with a pretentious air, calling himself a genius scientist, but frequently reveals a much more immature side. He is known for being extremely vindictive and holds a long-lasting grudge because Shintaro bullied him during their childhood. This obsession is so intense that he carries a diary everywhere to record every slight and humiliation he experiences. Despite his bitterness toward Shintaro, he addresses him with the familiar and affectionate name Shin-chan, similar to how Shintaro’s own father, Magic, does. Over time, his more childish and crybaby tendencies become more prominent, overshadowing his initial, more composed demeanor. One fan describes him as having a pure, almost innocent heart, even calling his smile a source of comfort in the series' chaotic world.

Within his organization, Gunma has established himself as a scientist, and he is often referred to as Doctor Gunma. He is responsible for creating various pieces of technology, including a line of battle mecha known as the Gumbot series. However, his designs often have critical flaws or are slightly incomplete, leading to them being described as lacking a finishing touch. Despite these shortcomings, he displays a genuine effort to learn from his mistakes and shows a broad-minded approach to technology, willing to use even low-tech solutions if they are useful. One of his key relationships is with his guardian and confidant, Doctor Takamatsu. Gunma trusts him completely, but Takamatsu has an obsessive and questionable affection for Gunma, often bleeding from the nose while watching over him. The pair are often seen working together, with Takamatsu supporting Gunma’s schemes.

One of the most significant aspects of Gunma’s character is his hidden family history. While initially presented as the son of Magic’s deceased younger brother, Ruser, it is eventually revealed that this is a lie. In truth, Gunma is the real son of Magic, the organization's leader, and the older brother of Kotaro. He was switched at birth with Shintaro (also known as Kintaro) by a vengeful uncle, meaning that Gunma grew up believing he was the nephew of his own father. Upon learning this painful truth, Gunma experiences significant mental anguish but ultimately achieves considerable emotional growth. By the events of the sequel Papuwa, he has come to accept his complex origins. He now refers to Magic as father instead of uncle and builds a more genuine, close relationship with his real brother Kotaro, as well as with both Kintaro and Shintaro, whose identities became entangled with his own. The members of his father’s organization, now under Shintaro’s command, still affectionately tease him, calling him the boss’s spoiled son. In the later series, his tastes in robots also evolve, moving away from purely battle-oriented machines to more fanciful creations shaped like animals such as elephants and ducks, further highlighting his more playful and less aggressive nature.