Ayumi Yamada, often called Ayu by her friends, is a central figure in the art college circle. When first introduced, she is a twenty-one-year-old student specializing in ceramic arts, and her talent in pottery is widely acknowledged, earning her high praise from her professors for works like a legendary bowl she created during her school years. Following her graduation, she chooses to remain at the college as a research student to continue her artistic development.

Outside of her academic life, Yamada is deeply involved with her family's liquor store in a local shopping district, where she helps her father and older brother run the business. Her upbringing in this environment has made her surprisingly strong, capable of moving heavy loads like thirty-kilogram blocks of pottery clay without difficulty. This physical strength, combined with a forceful and sometimes impulsive personality, has earned her the ironic nickname "Iron Man" among her peers, a stark contrast to her conventionally beautiful and delicate appearance.

Yamada presents a vibrant and energetic exterior, but this often masks a deeply emotional and vulnerable interior. She experiences intense heartache stemming from her long-standing, unrequited love for her close friend, Takumi Mayama. This emotional struggle is a core part of her character, leading to frequent moments of sadness and tears as she grapples with the pain of loving someone who does not return her feelings. Her primary motivation throughout much of the story is this love for Mayama, which becomes a bittersweet treasure she is reluctant to let go of, even as it causes her immense suffering. She often finds herself questioning why her experience of love feels so painful compared to the joyful portrayals she sees in media.

Within the story, her role is largely defined by this unrequited love, creating a poignant counterpoint to the other romantic entanglements in the group. Her feelings for Mayama are not returned, as he is persistently in love with an older woman, Rika Harada. This dynamic places Yamada in a painful position, watching the person she loves pursue someone else. Her key relationships include her close friendship with the shy and gifted artist Hagumi Hanamoto, who is one of the few people who shares her unusual palate for strange food concoctions. Her friendship with the eccentric Shinobu Morita is notable for its comedic physicality; she often reacts to his antics or her own embarrassment with violent kicks, a reflexive habit from her karate training, which Morita frequently becomes the victim of.

The most significant relationship in her life is with Takumi Mayama. He cares for her as a dear friend but consistently and gently rejects her romantic advances, even encouraging her to find someone else. This unrequited love is the central conflict of her personal journey. Her emotional development involves a slow, painful process of accepting this reality. For a long time, she clings to the hope that Mayama might one day see her differently, a feeling illustrated by her inability to "break the stem" of a damaged plant, hoping it might still heal. Ultimately, she begins to move forward, learning to let go of her bittersweet treasure. This development paves the way for a new relationship with Takumi Nomiya, a colleague of Mayama who patiently pursues her. In the end, she is able to accept Nomiya's affections, finding happiness with him later in life as they marry and settle in a home he builds for her, which includes a kiln for her pottery.

In terms of abilities, Yamada's foremost talent is her skill in pottery, which is respected enough to earn her commissions from the design firm where Mayama works. Her physical strength is notable, as is her proficiency in karate, which manifests in her powerful kicks. Conversely, she has a well-known weakness for alcohol, easily becoming intoxicated, and her culinary experiments are famously terrible, often mixing bizarre and incompatible ingredients that result in disastrous-tasting cocktails at school festivals.