In order to keep your samurai katana sword in pristine shape you need to do proper maintenance on it frequently. Typically it’s done every 2-3 months, usually depending on humidity in the area where you live. For example if you live by the coast you’ll need to clean and oil the sword even once a month due to saltiness in the air.
Don’t sweat though: just because you forgot to clean your sword for a month or two doesn’t mean it will automatically rust, but I do recommend you make sure you do it a minimum of once every 4 months. It would be a real shame to pay a few hundred dollars for a quality katana only to see it deteriorate without even using it.
Fortunately using a maintenance kit is very easy and the whole katana sword cleaning process lasts for about 10 minutes, perhaps a bit more if it’s your first time. You can watch the following 4 minute tutorial video showing you exactly how to disassemble a Japanese katana and perform the cleaning and maintenance process on it.
If you didn’t get a care kit when you bought your sword you can easily find some online for about $15 or less. When you buy and first open your maintenance kit you should make sure they contain a bottle of mineral oil called choji, a few napkins to clean the blade and get the old oil and dirt off, some rice powder and and special “baloon” called uchiko. The small hammer which is also included is used to remove the rivets by which the blade is attached to the tsuka (handle).
Hopefully by now you learned that even though quality katana need occasional maintenance, it’s definitely not hard or time consuming. This is the least you can do to show respect for the greatest sword made by man