Kid Niki: Radical Ninja, known in Japan as Kaiketsu Yanchamaru, is an arcade game developed and published by Irem in 1986, and was later published outside of Japan by Data East in 1987. The arcade game runs on Irem-62 Hardware, the same as Kung Fu Master.
The differences between the Kid Niki: Radical Ninja and Kaiketsu Yancha Maru are minimal. Aside from text translation, the most glaring difference is the main character's hair style. Kid Niki's hair is more "punk rock" with wild spikes and a ponytail in the back. Yancha Maru's hair has more subdued spikes and a topknot (or chonmage). In the arcade version of the game, the main character's keikogi is yellow while it is red in the home ports.
One day in Feudal Japan, Kid Niki, the most radical of ninjas, is training at his Ninja School. Suddenly, a passing bird is struck down by an arrow and lands at Niki's feet. Attached is a note explaining that Niki's girlfriend, Princess Margo, has been kidnapped by the evil Stone Wizard. With the cry of "Will help you!" Niki bursts through the wall of his school and sets off on his quest to save Margo.
Kid Niki is armed with the Spinning Sword, which according to the game's manual, "has been passed down from generation to generation from the School of Chirin."
In addition to the spinning sword, Kid Niki can gain extra offensive power by collecting Bells. The Golden Bell allows him to launch a projectile every time Kid Niki spins his sword, and the Silver Bell creates a spinning force field around him. Both of these power-ups last for a limited amount of time.