February 22nd is “Ninja Day” in Japan. It’s a play on words, as in Japanese, 2-2-2 is pronounced ni-ni-ni. The city of Koka in Shiga Prefecture is known as the birthplace of the ninja.

The association operates the Ninja Museum of Igaryu in Iga, a city famed as the home of the Iga ninja clan. In collaboration with Kyoto-based display coordinator Fujiya Co., the association plans ...