Honami Yasumoto serves as the microbiologist for the Antarctic Challenge Foundation's observation team. At the time of the expedition, she is still a graduate student who has not yet obtained her doctorate, which places her in an early stage of her scientific career. Her primary scientific ambition is to dive into the Antarctic seabed and discover something like a moss bed, a goal for which she harbors a burning passion.

In terms of appearance, Honami has ash-blonde hair that is typically tied back with chest-length strands hanging on either side of her face, and her eyes are blue-gray. Her wardrobe includes a long-sleeved pale pink sweater dress and ankle-length brown boots. One of her more notable physical characteristics is her lack of natural eyebrows, which means she has to draw them on, a process that takes additional time when preparing for things like interviews.

Her personality is something of a contradiction, blending her professional dedication with a more carefree and youthful side. While she is a serious researcher, her mental age is often described as quite young, and she is shown to be playful, happily joining the main group of younger girls in their games. Despite being regarded as a cute and attractive woman who is popular with men, she has no personal interest in romantic relationships. She also has a tendency to be an irresponsible drinker, as seen during her debut when she is quite intoxicated. Another quirky skill is her ability to make her own fermented alcoholic drinks, though the taste does not appear to be well-received by her fellow crew members.

Her role within the story is that of a supporting crew member on the expedition ship. She is first properly introduced to the four main characters when they interview her as part of their reporting duties. During the voyage, she shows concern for the girls, helping to secure their belongings in their room when they suffer from seasickness and warning them about the treacherous circumpolar current the ship is about to cross. She has a more active role in a scientific operation to discover sea ice, where the girls assist her. During this operation, she reveals a key connection to the past by telling them that Takako Kobuchizawa, the missing mother of one of the main characters, had helped her in the exact same location during a previous expedition.

One of her key relationships is with a fellow crew member, Sasaki Yume, who often looks after her. Honami wishes that Sasaki would wake her up earlier in the mornings, though she is known to be a very heavy sleeper who is difficult to rouse because she needs the extra time to do her makeup. Over the course of the journey, she does not undergo a dramatic personal transformation, but she serves as a reliable and approachable member of the scientific team, bridging the gap between the professional adult crew and the high school students. Her abilities are focused on her scientific expertise in microbiology and her specific passion for Antarctic marine life, as well as her practical knowledge of the ship and the harsh Antarctic environment.