黒漆太刀 Kokushitsu Tachi / Black Lacquer Long Sword

What is Kokushitsu Tachi in Japanese Katana terminology?

This is a long sword (Tachi) where the scabbard (Saya) is wrapped in leather made from animals like monkeys or horses, and then coated with black lacquer. This not only enhances the durability of the scabbard but also gives it a beautiful, glossy finish. The black lacquer also serves to protect the blade from moisture and rust.