To keep your katana in top condition: Store it in a dry environment, ideally in its scabbard (saya). Apply a thin coat of choji oil (or mineral oil) to the blade every 1–2 months to prevent rust. Avoid touching the blade with bare hands, as skin oils can cause corrosion. When cleaning, use a soft cloth to wipe from spine to edge, never edge to spine. If your sword came coated in a protective oil layer, this is normal — you can remove it with a soft cloth before display.