Ami Nonomura is the central character of the most popular story arc within the Cream Lemon franchise, with a narrative that traces her emotional and psychological journey from a young schoolgirl into adulthood. She is a high school student who is initially presented as a sweet and sensitive individual, though her experiences lead her through complex emotional landscapes.

Her background is defined by a deeply complicated family dynamic. Ami lives with her stepbrother, Hiroshi Nonomura, and their mother. The story begins when she enters a sexual relationship with Hiroshi, an act that is discovered by their mother, who then sends Hiroshi away to study in London as a consequence. This separation has a profound and devastating effect on Ami, who is deeply in love with her brother, leaving her in a state of depression. Seeking a distraction from her heartache, she is taken by friends to a nightclub, where she meets Ryuji Kouno, an older man with a reputation as a serial playboy. Under the influence of alcohol, Ami has a one-night stand with him, an encounter that Kouno seeks to repeat despite Ami's growing awareness of his superficial intentions.

As her story progresses, Ami is discovered and pursues a public career as a model and an idol singer. While she achieves recognition, she feels disconnected from this work, finding that it does not reflect her authentic self. This period of her life is also marked by escalating tensions within her family, including her father proposing a divorce from her stepmother, and strained communications with her own mother, who offers criticism rather than support. The return of Hiroshi to Japan for a brief visit provides a moment of hope, but it instead brings further devastation when he informs Ami that their romantic relationship must end. Throughout these trials, Ryuji Kouno remains a persistent figure, even rescuing her from an assault by a photographer during her modeling career, but Ami consistently recognizes his inability to see her as anything more than an object of desire.

Ami's character development culminates in a decisive turning point. Her friends plan a trip to Hokkaido to celebrate her birthday, but while gathering her belongings, Ami discovers a book titled "First Love" in Hiroshi's room. Inside, she finds an old photograph of herself with a handwritten note from Hiroshi expressing his conflicted feelings about their sibling relationship. Recognizing his unresolved feelings and confronting her own desires, Ami makes a choice that signifies her transition into adulthood. Instead of joining the trip to Hokkaido, she abandons that plan and travels to London to confront Hiroshi and resolve their relationship on her own terms. This act represents a shedding of her insecure adolescent identity and a determined pursuit of her own path. Her story concludes years later, where she has grown into a young woman still working as a popular idol, but continues to grapple with where she stands in her relationships with both Hiroshi and Kouno.