I'd like to think of this as when Kotaro is a little older. At least 1st grade. He sees Mozzy being picked on by some bullies, and he's not having that. He's making it clear that if they want to hurt his friends, they have to go through him first. His father's forbidden him from actually fighting, but he can at least get them to back off.

Kotaro is to me
Mozzy is to  blueratmatt