The most striking example of Pierrot flair is actually the 'jutsus' which are SIGNIFICANTLY developed from the main series. In the actual series it's one, or two signs, but at times they really expand the handsigns into more complex chains that often end in the same signs we see in Naruto. The fire jutsu ending in two open hands to the side is specifically something we see in Naruto, and it's unclear if that even came from the Ninku manga or Pierrot came up with that themselves. It's very obvious, and Kishimoto has stated, that he was inspired by Ninku so it's almost guaranteed he was watching this movie as the basis for much of early Naruto's combat. While the pull from Ashita no Joe is clear, the actual choreography in this movie is phenomenal and really leans into a development of Ninja-shounen combat diverging from previous ninja series. More focused on a back and forth found in works such as Dragonball, less death-strikes seen in the previous Ninja works up to this period.
Even the ending of this feels like something you would see in Naruto, avoiding spoilers, you can see how Fuusuke really shines and stands out as the emotional core of this series. It's incredibly wholesome. Such a short 'episode' is hard to comment on extensively, but this is something I'd recomend any Naruto or Shonen fan to give a watch even if they haven't seen Ninku prior. It's some of the best historical exposure to the series you can find.
