Every knife would gradually lose its sharpness after using for a while. By regularly taking care of your knife, the sharpness would reappear and keep the blade in good condition. When you cannot easily cut a tomato, it is a sign that your knife needs to be sharpened. We recommend you to sharpen your knife with a whetstone. It may need some practice to use whetstones, though you can create a sharp edge on the blade and keep the sharpness for long time. If you do not use a whetstone, please use a convenient sharpener. When you use sharpeners for daily care, we recommend you to have your blade sharpened with a whetstone once a year by knife sharpeners in stores.