Jaiko Goda, also known as Geganteta in some Spanish dubs and as Little G in English adaptations, is the younger sister of Takeshi "Gian" Gouda. She lives in Tokyo and is approximately eight to nine years old, with her birthday falling on July 19. Her physical appearance mirrors that of her older brother, as she is a short and chubby girl with short black hair. Her typical outfit in the earlier anime adaptation consisted of a red overall skirt with a white top and a beret, while in the 2005 anime series, she wears a green top with a flower design and retains a hat associated with her passion for manga.

The character of Jaiko underwent a significant evolution in personality from her first appearance. Initially, she was portrayed as snobby and mean-spirited, often taking pleasure in playing pranks on Nobita Nobi. This early characterization was short-lived, and in the vast majority of her subsequent appearances, she is consistently depicted as a kind, considerate, and gentle girl. This revised personality, which stands in direct contrast to her brother Gian's aggressive and hot-blooded nature, became the standard for the character and remained unchanged in the 2005 anime remake. Her original, less pleasant traits were largely reassigned to the rarely seen character Botako.

Jaiko's primary motivation and the central focus of her character is her dream of becoming a professional manga artist. She is highly skilled in domestic areas like cooking and sewing, but her true passion lies in drawing and writing comic books. She pursues this ambition under the pen name Christine Goda, diligently submitting her work to publishing companies for contests and prizes. Despite her enthusiasm and effort, her storytelling skills are often described as underdeveloped or rough, leading to frequent rejections. These failures cause her to frequently consider giving up on her dream, a situation that forces her brother to coerce his friends into cheering her up. Despite these early struggles, it is established that in the future, Jaiko will eventually achieve great success, becoming a famous and wealthy manga artist with high sales.

Her relationships with other characters are central to her role in the story. Her most defining relationship is with her brother, Gian. While they experience typical sibling conflicts, they get along very well. Gian is extremely protective of Jaiko, to the point where he reacts aggressively to any comments made about her by others, particularly Nobita. He is known to use Doraemon's gadgets to assist her with her manga ambitions, and he forces his friends to encourage her whenever she feels like quitting. Within her family, her mother treats her more favorably than Gian due to her good behavior, assigning her fewer chores in the family store. Her interactions with her father are less frequent, though their relationship is presumed to be positive.

Jaiko also has a notable background concerning the series' original timeline. In a future that was later altered by the arrival of Doraemon, Jaiko was destined to marry Nobita. This potential future is glimpsed in a story where Nobita, using a gadget, sees a vision of Jaiko beside him at an altar. This caused significant distress for Nobita, until it was revealed that the ceremony was not a wedding but a commemoration for the sale of millions of copies of her successful manga. She has also experienced romantic interests, including a past crush on a boy named Motesugi and later developed feelings for a seventh-grade student named Moteo Mote. She is occasionally referred to by the name Hana.