Imagine how ****ing good this movie would be if it was directed by gareth evans
t:It infuses the character.
He's clearly aping the something he saw/read in a samurai book. I'd imagine he's the type of teen that watched one to many kurosawa films or maybe it has something to do with how spinter dresses. The point is, this isn't a matter of why batman decides to wear a cape or why spidey has rubber soles on his feet in ASM. This is almost 100% characterization work seeing as they are choosing what they want to wear and obviously need none of it.