This is what happened to one of my Takayuiki knives. I have always cleaned them and dried them after each use even though I bought these knives as non staining/rusting. I bought a 300$ Moritaka from Paul's and returned ir after two days of staring at it because of being affraid of issues like that. I've had them for three years, using it once a week. Knives were left in a pot filled with water after slicing a mild sausage and green onions.