The Japanese concept of swords is quite different from that of people in other parts of the world, who often regard a sword as a whole, including the handle, sheath, and guard.
However, the Japanese view the sword and its fittings separately, believing that the blade itself is the sword, while the fittings are just its clothes. Therefore, they usually keep the blade in a white sheath, only wearing a full set of fittings when going out.
The so-called white sheaths are often made of naturally dried crude wood. Since crude wood contains less resin, it is less likely to damage the sword itself.
A full set of fittings requires lacquering, so the sword inside is kept in a completely sealed environment. This is what Japanese sword collectors call a "suffocated" long-term environment, which is more prone to rusting.
