Are ninjas Chinese

Answer 1

Japanese.

But...

The roots of the Japanese Ninja lie in the fertile grounds of Historic China. They belong to The Lin Kuei. Lin Kuei (or Lin Gui - 林鬼 in Mandarin) is a Mandarin Chinese term meaning forest ghosts. Martial Arts historians and others researchers have postulated such a group existed in the forests of China many years ago. This would have been long before the ninja emerged in Japan.

Tales of Lin Kuei have disturbed travelers and peasants for centuries. They were rumored to be night-dwellers possessing mystical powers. This mythical shroud of true identity precisely parallels the methods of the Japanese Ninja. The Ninja of Japan used secrecy, rumor, demon masks, and pyrotechnics to ignite man's combustible innate fear of the unknown, overcoming adversaries psychologically first and foremost. As a result of the Lin Kuei's way of utmost secrecy, very little beyond ancient stories and rumor exists today to shed a light on their society.

Approximately during China's Tang Dynasty, some of the Lin Kuei members traveled to Japan and diffused their secret martial arts and ways to the locals. These methods were eventually incorporated into the art of ninjutsu. It is believed that some Lin Kuei stayed in Japan and made a living as mountain hermits or priests, known as the Yamabushi (those that hide in the mountains). The term refers to isolated clusters (or individuals) of mountain hermits, ascetics, and "holy men", who search for spiritual, mystical, or supernatural powers gained through asceticism. Other Lin Kuei traveled to Korea and continued their teachings.