Determined to eradicate all the birds whose songs and cooings annoy him, Ashida breathes life into the statue of a legendary falcon hunter who once served his terrible ancestor Atsumori. The mini-ninjas will therefore have to prevent him of causing trouble.
It's winter and Ashida has decided to build an onsen (a Japanese thermal bath) on one of the hot springs in the area. To do this, he created tailor-made workers: Samurai with six arms, resistant to the heat given off by the springs and capable of taking down the work of ten infantry! But the spring he wants to appropriate is also the winter bathing place of the monkey families of the valley. Deprived of this heat, the poor monkeys are doomed. To save them, our heroes have only one solution: defeat these monstrous "Centipede Samurai"!
Showing himself too impatient, Hiro is entrusted with the chore of putting away the Master's scrolls to learn patience. That's when he discovers a scroll unlike any other, fitted with a clasp to prevent it from opening accidentally. Intrigued, Hiro unrolls it and frees Sanjoru, a ninja ghost who declares to be a great hero who was a long time ago trapped by the parchment.
When Hiro boasts that he could take over as ninja master one day, the Ninja Master takes him literally and offers to let him take over for a day.
