The latest from Grand Seiko is a pair of watches designed for ninja, the covert warriors of feudal Japan known for their silent and deadly skill.

Made of steel and polished with the Zaratsu technique, the shuriken-shaped bezel on the men’s Grand Seiko Ninja has razor-sharp edges. But according to Seiko, “Fear not; [the] watch will never accidentally scratch or hurt anyone.

Powered by the cal. 9R65, the Spring Drive movement “combines the strengths of both mechanical and electronic watches, like a ninja with two swords.” In addition, the glide wheel regulator of the Spring Drive ensures it operates silently, so “Spring Drive will never betray you during your clandestine operations.”

Conceived for women ninjas, the’ Grand Seiko Kunoichi watch is in 18k rose gold, with the shuriken bezel set with diamonds, and an automatic movement. Seiko says it is “shaped and polished to deliver when it really matters.”

Both are of course an April Fool’s joke courtesy of Seiko, which also set up a microsite for the ninja timepieces. The shuriken watches follow last year’s Prospex canned tuna.