Part of the exhibit Dressed to Kill: Japanese Arms & Armor at the Cincinnati Art Museum. I love Japanese culture, and their swords in particular, so I had to visit. From the description:
Large ken, like this one, were once used as weapons by yamabushi, religious hermits living in seclusion in the mountains. Provincial lords hired yamabushi as couriers of secret messages because they could travel undetected throughout Japan on mountain routes known only to them. Yamabushi also fought alongside samurai in battle. Some became professional spies, known as ninja.