This is a delightful historical fiction if you're into this.

https://en.wikipedia.org/wiki/The_Thousand_Autumns_of_Jacob_...

Also there's a museum. It's on my list!

https://www.niche-museums.com/59

Supplying high grade explosives and ammunition was seen as a way to profit from potential conflict, which eventually made the Shogun wary of their presence.