: Mawari begins to suspect Sun's true nature after she briefly glimpses Sun's mermaid tail following a water-related accident at school.

: The episode introduces Mawari Zenigata , Nagasumi's childhood friend and the strict leader of the school's Disciplinary Committee.

: Mawari eventually uses cats to try and startle Sun into revealing her true form. However, she relents after seeing how much her aggressive tactics genuinely upset Sun. Character Introductions

: Sun Seto and the tiny, shell-using assassin Maki follow Nagasumi back to his family home in Saitama. Nagasumi is humorously ousted from his own room and forced to live in the attic so Sun and Maki can stay in his bedroom.

: Though her role is minor in this specific episode, she appears as a recurring background character often involved in the school's chaotic events.

: A disciplined student and the daughter of a police officer, her presence adds a new layer of tension as she constantly monitors Nagasumi and Sun.