It was through a series of unfortunate events, during WWII, that the Japanese history, particularly the tradition of their swords, came into prominence. Classifying Japanese Swords has been an extremely debated subject and it still engages many conflicting views. For the uninitiated, a Japanese sword represents a technical innovation that was at least a century ahead of its generation. Unlike swords used in other parts of Asia and the Western World, it was able to combine three parameters deemed incompatible by most sword-makers, i.e. being indestructible, having intense slicing capability and uncompromising firmness. Further, Japanese swords were able to blend these qualities and yet present the sword as a distinctly maneuverable weapon.
Historically, the Japanese people have always looked upon their swords as a symbol of personal and family pride. Even the basic etiquette regimen in just carrying a sword is so demanding that it takes years for one to comprehend it. It is believed that the Samurai warriors were so obsessed with protecting their swords that they would try to breathe at a certain distance away from the top blade, ensuring that no moisture would touch upon it. Therefore, it only seems fair that contemporary collectors of Japanese swords are familiar with the basics of such revered objects, considering that these aren't just artifacts but symbols of a proud legacy.
Japanese Sword Care Basics
Often called the Nipponto, every Japanese sword has a scabbard or the casing, also called the saya. Swords are often presented in wooden sayas and many of them are adorned with handcrafted embellishments. Collectors should ensure that the head of the saya, called the kojiri, should always be the first to enter the casing. Though this is regarded as a way to prevent damage from accidental falls, it also represents a mannerism endorsed by generations of Samurai warriors.
The scabbard should tightly fit around the sword, particularly around the opening. If this is not so, chances are that the sword under consideration has been excessively tampered with. Around the opening of the scabbard is the collar or the Habaki of the Nipponto. When pulling out the sword, ensure that the sword is first partially drawn, i.e. at par with the length of the Habaki. Only then, the sword should be completely pulled out. A single, forceful pulling can be extremely damaging and it can harm the collar configuration beyond redemption.
Once the sword has been partially pulled, the blade has to be held firmly, ensuring that the slicing edge does not face either sideways or downwards. This is not only the preferred method of pulling the sword from a preservation perspective but also a traditional custom of Japanese swordsmanship. This is also the safest, forward-holding position for drawing out the Nipponto. When placing back the sword into its scabbard, the tip of a sword, with its cutting-edge pointing up, has to be rested gently on the scabbard's opening for a moment before being firmly pushed-in. When doing so, feeling an obstruction around the collar is expected - a small, firm nudge is needed to make the sword edge past the collar and slide inside its casing.
from
https://www.katanasale.com/blogs/katanasale/antique-swords-an-introduction-to-japanese-swords-their-preservation