Eiko Aizawa, a high school student with auburn hair and amber eyes, serves as the diligent deputy manager of Lemon Beach House, a seaside restaurant she co-runs with her older sister Chizuru and younger brother Takeru. Often clad in the establishment’s uniform, her short temper flares when disruptions arise—especially those caused by Squid Girl, whom she initially dismisses as a nuisance. Though academically challenged, Eiko prioritizes restaurant duties over schoolwork, frequently choosing video games over textbooks during downtime. Her dynamic with Squid Girl shifts from reluctant caretaker to mutual reliance after the latter damages the restaurant’s wall. Eiko compels Squid Girl to work off the debt, sparking frequent clashes. Yet their bond deepens through collaborative efforts like volleyball matches and Eiko’s visible concern during Squid Girl’s temporary departure. A pivotal moment cements their connection: Squid Girl regenerates tentacles to rescue Eiko from drowning, underscoring their transformed relationship. Eiko shares a close childhood friendship with Sanae Nagatsuki, though she’s unnerved by Sanae’s obsessive admiration for Squid Girl. She playfully needles Gorō Arashiyama, a family friend and lifeguard, about his unspoken affection for Chizuru. Protective of her siblings, she keeps a watchful eye on Takeru during his playful exchanges with Squid Girl. Despite her stern exterior, vulnerabilities surface—she’s ticklish on her feet, sides, and belly, and begrudgingly accommodates Squid Girl’s presence in her home and life. As the pragmatic counterbalance to Squid Girl’s chaos, Eiko strives to maintain order at the restaurant. Brief role swaps with Ayumi Tokita and navigating language barriers with Cindy Campbell hint at an adaptable side. Though her wardrobe sees minor seasonal changes, these details remain peripheral to her unwavering focus on managing the restaurant’s daily tumult.