The sharp edge of a katana is located on the outer curve of the blade. This side is traditionally referred to as the "ha" in Japanese. It is important to note that the edge is only sharp along a portion of the blade's length, typically from the base to the tip, while the rest of the blade is not sharpened and is known as the "mune" or spine.

The sharpened edge of a katana is carefully crafted by a skilled swordsmith using specialized techniques. The sharpness of the blade enables the katana to cut effectively while maintaining its strength and durability.

When handling a katana, it is crucial to exercise caution and always be mindful of the sharp edge to prevent accidental injury. Proper training and knowledge of katana etiquette and handling techniques are essential for safely wielding and using a katana.