Dressed in black martial arts uniforms and wearing split-toed tabi footwear, around 60 students are performing various grappling and throwing techniques inside the 520-square-meter Budojo 1 at the Tokyo Budokan, a massive martial arts arena in the Ayase area of Adachi Ward.

The venue hosts a wide variety of martial arts training, but when I visited one night years ago, the tatami-floored Budojo 1 was entirely dedicated to the Bujinkan, an organization that is most strongly associated with authentic ninjutsu, the combat and stealth techniques used by ninja.

That night, the students were under the watchful eye of Bujinkan founder Masaaki Hatsumi. He presided over a sakki test, in which students deemed “ready” had to sit with their eyes closed and evade a strike from a bamboo sword — some succeed to considerable collective excitement. One thing that stuck out about the class, though: Despite a handful of Asian faces, the ninja student body was largely a sea of white men.