S1·E14 A Kitten's Story

Nagasumi finds a kitten and brings it to school. Nagasumi soon discovers that Sun, Lunar, and Maki are all deathly afraid of cats, and gets the idea to test it on Kai and Gōzaburō too, but before that learns that most mermaid adults are not afraid of cats anymore as they eventually get over their fear; this however does not apply to Gōzaburō due to a tragic experience as a child. Nagasumi decides to make this into an advantage.