Ginko Echigoya, whose name means "silver child," is the younger sister of Kinko ("golden child"), reflecting their wealthy Echigoya family background. This 9-year-old attends the same elementary school as Asu Yamada and serves as a class representative for a parallel class. Ginko has yellow or blonde hair, cyan eyes, and typically wears practical clothing.

Initially arrogant and domineering, Ginko's blunt demeanor and sense of superiority make her less popular than Asu and hinder her relationships. She operates under considerable pressure to match her accomplished older sister's example, whom she deeply admires yet fears disappointing. This pressure includes participating in Kinko's baffling bargain-hunting excursions despite their family's wealth. Misunderstandings and emotional distance define the sisters' relationship, with each mistakenly believing the other resents them. A unique element of Ginko's life is her pet alligator, John, kept in their garden and adorned with an oversized ribbon.

Ginko's character development stems from secretly observing the supportive bond between the Yamada sisters. This exposure fosters her gradual understanding of sisterly connection, ultimately helping her reconcile with Kinko. Their improved communication leads to a patched relationship, marking Ginko's journey from insecurity and social awkwardness toward a more aware appreciation of familial bonds.