A New Ninja Technique (The ninja battle) (新忍法の道けわしの巻) is episode 512 of the 1981 Ninja Hattori-kun anime.
Kemumaki and Hattori are duelling each other in the waste ground with cannonballs. Even though Kemumaki comes up with new ninja techniques, he is no match for Hattori. Ding Ding!
Kemumaki and Hattori are standing in the waste ground, ready to fight each other with cannonballs. The duel starts, and Kemumaki puts up a good show, but Hattori defeats him with a certain Ninja Technique called the continuous throwing with two hands ninja technique. After the battle, Kemumaki commiserates whilst walking down the street - but then he sees a picture of a deity with several hands. After some critical thinking, he creates the throwing with multiple hands ninja technique.
The next day, Kemumaki and Hattori have a rematch. Kagechiyo comes along, asking if Hattori is going to use the same ninja technique. He is proven right. Afterwards, Kemumaki uses his new ninja technique, catching all of the cannonballs with his auxiliary hands. He throws back them back to Hattori and Kagechiyo gives him some more. Kemumaki then throws a smoke bomb and a cannonball at Hattori. Unbeknownst to Kemumaki, Hattori escapes from his robes while Kemumaki throws the smoke bomb at him, and catches them, throwing them back at Kemumaki and Kagechiyo. Back at their home, Kemumaki and Kagechiyo bandage themselves. Suddenly, Kemumaki comes up with an idea.
Twenty-four hours later, Kemumaki and Hattori fight again, only this time Hattori is being aided by Shishimaru, and Kenichi and Shinzo are hiding in a bush. Hattori has got another fly in his ointment as Kemumaki has attached another set of auxiliary hands to his stomach, remote controlled by Kagechiyo. Just then, Kemumaki sees Kenichi and Shinzo, and throws a large cannonball at them. Hattori saves them from impending doom and uses the Bowling technique to defeat Kemumaki. It also hurts Kegichiyo, who drops all the fireballs they had onto themselves, resulting in an a gigantic explosion. The episode ends with Hattori and his friends watching Kemumaki's defeat.