Gin Tōdō is the female leader of a civilian Antarctic observation team known as the Antarctic Challenge. Her journey to the frozen continent began decades ago in high school, where she became close friends with Takako Kobuchizawa. It was Takako, who dreamed of going to Antarctica, who invited Gin to pursue this seemingly impossible goal. This friendship, which started in their youth, would become the central axis around which the rest of Gin's life would revolve.

In terms of personality, Gin is defined by her quiet and reserved nature. She is a woman of very few words, which can sometimes lead others to misunderstand her intentions or mistake her silence for coldness. Despite her lack of loquaciousness, she possesses a powerful and commanding aura that inspires deep trust and respect from her team members. She is a decisive leader who can remain calm under pressure and make quick, reliable judgments in the perilous conditions of the polar environment. While she appears strict and authoritarian at first, this is a result of her deep-seated sense of responsibility and her commitment to the safety of the expedition.

Gin's primary motivation is intertwined with a profound sense of guilt and duty. Three years before the main story, Gin was part of a previous Antarctic expedition alongside her best friend, Takako. During that mission, Takako went missing and was presumed dead. Gin was the last person to receive a communication from her friend before she vanished, and she has carried the immense weight of that loss ever since, feeling a deep responsibility for not being able to bring her back. This tragedy caused sponsors to pull their funding and left the future of the Antarctic Challenge in jeopardy. Gin continues to lead the new expedition not just as a job, but as a personal mission to honor Takako's memory and to confront the place where she lost her.

Her role in the story is that of an anchor and a conduit to the past. She serves as the experienced captain and instructor for the main group of teenage girls, including the main protagonist Mari Tamaki and her friends. Gin’s presence on the icebreaker ship and at the Showa Station is a constant reminder of the expedition's true purpose and its tragic history. Because Gin handles the external negotiations and communications for the team, as she is not comfortable with public speaking, her partner Kanae Maekawa manages most of the interactions with sponsors and the outside world.

The most significant and complex relationship in Gin's life is with Shirase Kobuchizawa, Takako's daughter. Gin has known Shirase since she was a small child, often being tasked by Takako to look after her. This created a bond between them, but one that was shattered by the disappearance of Shirase’s mother. Before the events of the series, Shirase harbored a bitter resentment toward Gin for returning from Antarctica without her mother, creating a painful rift between them. Throughout the series, much of Gin’s development involves her attempts to bridge this gap and finally confront the truth of what happened with Shirase, ultimately finding a way to provide closure for both of them by delivering a final, heartfelt message from Takako.

Regarding her abilities, Gin Tōdō is a highly skilled leader and accomplished explorer. Her experience is crucial for navigating the dangers of Antarctica. In addition to her leadership skills, she is noted to be an excellent baseball pitcher, a skill that reveals a more playful side and allows her to connect with the younger characters on a more equal footing late in the series. She also taught Shirase how to skip rope when she was a child, showing that her abilities extend beyond survival skills into the small, meaningful gestures of care. Her most notable ability, however, is her resilience; the strength to carry the burden of her past mistakes and grief while still guiding an entire team toward a dangerous goal.