Nagisa Saitō, a recurring human character, works part-time at the Lemon Beach House restaurant alongside the main cast. She has tan skin, short indigo or dark blue hair, gray eyes, and an average height. Her older sister, Aiko Saitō, is an elementary school teacher and Takeru Aizawa's homeroom teacher. Nagisa attends high school but not the same institution as Eiko Aizawa or Sanae Nagatsuki. Introduced as a surfer, she joined Lemon Beach House partly to access more surfing opportunities. Her skills include bike riding and jump roping, and she spends spare time watching magical girl and tokusatsu television shows. Unlike other characters who humorously dismiss Ika Musume's threats, Nagisa genuinely fears Ika as a legitimate threat to humanity. This fear persists through her appearances, though she intermittently tries to overcome it. Once, she combed her hair backward to disguise herself as a male, aiming to deter Ika's teasing and attract female customers, but abandoned the effort after concluding she must acknowledge Ika as an invader. Another time, she pretended not to fear Ika until panicking and fleeing when forced to shake Ika's hand. Nagisa considers coworkers Eiko and Chizuru Aizawa unusual for treating Ika normally. She remains wary of Ika's actions, interpreting them as part of an ongoing "Inkvasion" plan. This suspicion occasionally escalates, such as when she attacked Ika after being hugged. Friends Koike and Yamada, introduced later in the manga, visit Lemon Beach House, though their interactions lack detail in the anime. Nagisa consistently wears the restaurant uniform during work and a black bodysuit for surfing. Her expressiveness and reactions, particularly toward Ika, define her appearances.