Chihiro is troublesome little boy. He likes to throw frogs at people.
POV: The enemy leader is afraid of your pet frog.
Mikado, Red Shadow (also known as Hotarubi), Jo, and Hongou all react to this frog in this over-dramatic way. This behavior is tied to their movelist, so any character can be made to react this way.
POV: A grown woman, who is also a samurai assassin (and might be able to hear the dead), is afraid of your pet frog.
POV: You found the only ninja that doesn't like frogs.
POV: That one girl in class thinks she's so cool.
POV: You found the guy that's bullying your brother.
POV: That girl came back! She's friends with the bully!
In their defense, it's a big frog. It also continues to move around the stage and can jump off ledges. It is a pain to pick back up in first person mode.
Further, nothing is stopping any character from picking the frog up and throwing back into Chihiro's face.