Arisa Uotani endured childhood neglect after her mother departed with a boyfriend, leaving her with an alcoholic, emotionally distant father. This environment drove her to join the all-female gang "The Ladies" in fifth grade, plunging her into violence, theft, and delinquency. During this time, she idolized the legendary gang leader Kyoko Honda, "The Red Butterfly," renowned for her strength and moral code. Learning Kyoko's daughter, Tohru Honda, attended her middle school, Arisa sought her out, anticipating someone equally fierce. Instead, she found a gentle, optimistic girl. Initial disillusionment followed witnessing Kyoko's transformation into a doting mother. Though she initially rejected their kindness, Arisa gradually bonded with Tohru after Tohru rescued her from a gang beating. Kyoko later intervened to save Arisa when she was brutally beaten for leaving the gang, cementing Arisa's resolve to reform. She resumed schooling to stay near Tohru and befriended Saki Hanajima, forming an inseparable trio. After Kyoko's death, Arisa and Saki swore at her grave to protect Tohru, with Arisa adopting a brash, direct "father-figure" role.

Arisa exhibits a tough, tomboyish exterior characterized by blunt speech, including using the masculine pronoun "boku." She often carries a lead pipe and displays a fierce temper, especially confronting threats to Tohru like the Prince Yuki Fan Club. Despite this aggression, she is emotionally expressive, crying easily over sentimental situations like elderly people buying convenience store meals or Tohru wearing an old swimsuit. Her loyalty to friends is profound. She leverages her past to mentor wayward youth, earning the respectful title "Ane-sama" from a trio of former delinquents. She maintains a competitive, bickering relationship with Kyo Sohma. While her home life remains strained, she actively manages her father's alcoholism, limiting his drinking during holidays.

Working part-time at a convenience store, Arisa met Kureno Sohma, feeling an instant attraction despite concerns over their nine-year age difference. After a second encounter where Kureno nearly kissed her, he withdrew, bound by a promise to Akito Sohma. Arisa tried to move on. When Kureno later left Akito, she helped him relocate from the Sohma compound, declaring she had waited. Their relationship progressed, and by the series conclusion, she prepared to move in with him. Her appearance evolved, featuring shorter, shoulder-length hair without bangs covering her eyes.