Takeshi Gouda, universally called Gian, is a central figure across Doraemon media. He lives with his parents and younger sister, Jaiko. His mother runs a grocery store and wields significant authority over him, frequently punishing his misbehavior physically, an outcome he intensely fears. Gian demonstrates strong protectiveness toward Jaiko, actively supporting her comic-writing endeavors, though his approach often frustrates her. He owns a dog, Muku, primarily tended by Jaiko, though Gian sporadically shows concern for the animal.

Gian's personality blends aggression with surprising depth. His defining catchphrase, "What's yours is mine and what's mine is mine," underscores his bullying nature, especially targeting Nobita and Suneo. He habitually confiscates toys, manga, or gadgets under the guise of borrowing them. He exhibits extreme overconfidence in his notoriously poor singing and cooking abilities, forcing others to endure his concerts or taste his creations, causing widespread distress. Despite his domineering behavior, he displays fierce loyalty and protectiveness during genuine crises, frequently aiding friends in perilous situations across films and episodes. He also reveals vulnerability, crying during emotional moments or reflecting on his unpopularity after events like birthday rejections. Possessing superhuman physical strength classified as "Wall level," his destructive singing reaches "Small Building level," occasionally utilized as an unconventional weapon.

His relationships are complex and evolving. Interactions with Nobita primarily involve intimidation and abuse, justified by Gian's belief that bullying Nobita is essential to his daily life. Yet, moments reveal underlying ambivalence, including robotic alter egos expressing mutual friendship desires and Gian rescuing Nobita or aiding Doraemon in life-threatening situations. Suneo serves as his frequent accomplice and messenger, though their friendship is uneven, marked by Gian's occasional aggression toward Suneo and Suneo's covert rebellions using borrowed gadgets. Gian respects Shizuka, often heeding her admonitions against bullying, though he once reacted violently discovering her gadget use to curb him. His dynamic with Doraemon involves both coercion for gadget access and mutual cooperation, especially concerning Jaiko or community threats.

Character development unfolds through episodic and film narratives. While often an antagonist, his role expands to show redeeming qualities, like leading his baseball team, the Giants, where he tolerates Nobita's poor athletic skills out of necessity. Stories explore his self-awareness, such as an episode where Doraemon's lecture prompts a temporary reform effort, though peer mockery triggers regression. In specific adventures, like veterinary practice attempts, he displays earnestness helping animals despite comical ineptitude, later abandoning the pursuit to refocus on singing. His protective instincts surface in film crises, preventing Nobita from falling or aiding group survival in treacherous environments, highlighting his capacity for teamwork and sacrifice. These portrayals contribute to his multifaceted identity.