Well, a lot of DC series have ninjas on them. Although, I'm a little bit dissatisfied but this manga have a full privilege to have a real ninja on them. Looking forward to the next chapter, I hope this arc will be interesting.
@Confetti Western Superheroes have ninjas. Daredevil's most well known adversaries is a secret ninja organization called the Hand, and Batman's current Robin was raised by a secret assassin clan.
Honestly, I'm excited the mangaka is going all out with superhero weirdness. Can't wait for Lex Luthor to show up and use capitalism to ruin everyone's day.
This just got stupider.
Just because regular superhero comics regularly dip into rampant idiocy for the sake of drama doesn't mean it is an example that should be copied. It is better to explore what you have already in more depth than to just introduce new elements out of the blue.