Takeshi Goda, universally known by his nickname Gian, is a central figure in the neighborhood where the story takes place, recognized immediately by his large, imposing stature, tan skin, and black hair. His nickname, derived from the English word giant, perfectly encapsulates his role as the local bully who uses his immense physical strength to dominate and intimidate the other children. He frequently takes toys, comic books, or even advanced gadgets from Nobita and his peers, always under the pretext of borrowing them, a claim enforced by the threat of violence.

Gian's personality is a striking contradiction of aggressive bullying and unexpected loyalty. On the surface, he is quick-tempered, overbearing, and convinced of his own superiority in areas where he has no talent. He is famously oblivious to his dreadful singing voice and terrible cooking, forcing his friends to endure his concerts and taste his food under duress. He is also the self-appointed captain of the local baseball team, the Giants, where he constantly blames Nobita for the team's frequent losses yet forces him to continue playing. The motivation behind this antagonistic behavior is multifaceted; he openly claims he cannot eat or sleep if he does not bully Nobita, suggesting a deep-seated, albeit twisted, dependency on his role as the neighborhood's top bully.

Despite this fearsome exterior, Gian possesses a clear and often-explored softer side, which frequently emerges in moments of genuine crisis. He is deeply loyal to his younger sister, Jaiko, and becomes fiercely protective of her, often helping her with her dream of becoming a manga artist. The only person who truly terrifies him is his mother, who runs the family grocery store; her anger is the sole force capable of instantly stopping his rampages and reducing him to a state of cowardly submission. This complex core is central to his role in the story, as he alternates between being the primary source of Nobita's daily despair and, in the feature-length films, a surprisingly reliable and brave ally who does not hesitate to risk his safety for his friends.

In the specific narrative of Stand By Me Doraemon, Gian's role as an antagonist is crucial to the plot's emotional core. His relentless bullying of Nobita is a primary contributor to the bleak future that Doraemon was sent to prevent. The film reaches a pivotal climax when Nobita decides he must prove his self-reliance by challenging Gian to a physical fight. Gian initially overpowers Nobita with ease, but he is ultimately moved and exhausted by Nobita's unwavering refusal to give up. Recognizing the smaller boy's incredible determination, Gian forfeits the match, showing a moment of reluctant respect and acknowledging a strength that is not physical. At the film's conclusion, Gian engages in an April Fools' Day prank, falsely telling Nobita that Doraemon has returned. This act prompts Nobita to use a truth-reversal gadget in retaliation, which inadvertently leads to a series of events that ensure Doraemon's permanent return, demonstrating how even Gian's negative actions can have positive consequences in the story's intricate timeline.

Gian's key relationships define his daily existence. His friendship with Suneo Honekawa is one of convenience and fluctuating power, with Suneo often acting as a sycophantic sidekick to avoid Gian's wrath, though their alliance can easily crumble. His dynamic with Shizuka Minamoto is notably different, as he rarely bullies her directly and will often cease his aggressive behavior when she intervenes. His relationship with Nobita is the most complex and developed; it is a volatile mix of tormentor and protector, where Gian can be both the cause of Nobita's tears and the one who offers him medicine when he is sick or saves him from a genuine danger.

Over the course of the broader narrative and specifically within the film, Gian shows subtle but significant development. There are moments of introspection where he realizes his unpopularity and makes sincere, though often failed, attempts to change his behavior. His repeated failures to reform, often foiled by his own uncontrollable temper or the mockery of others, add a layer of tragicomedy to his character. However, his future self is consistently portrayed as a matured individual who grows into a responsible father and a successful business owner, suggesting that the good heart that occasionally peeks through his brutish exterior is his true nature. His notable abilities include his phenomenal physical strength, his terrifying singing voice which is occasionally used as a weapon, and his leadership of the neighborhood baseball team, where his aggressive spirit can sometimes inspire his teammates despite his lack of strategic skill.