Yes, katanas, the traditional Japanese swords, often have a fuller, also known as a "hi" in Japanese. A fuller is a long, narrow groove that runs along the blade's length, typically on both sides of the blade. It is designed to reduce the weight of the sword while maintaining its strength.

The fuller in a katana serves multiple purposes. Firstly, it helps in distributing the weight of the sword, making it lighter and more manageable. This allows for faster and more agile sword movements. Secondly, the fuller enhances the structural integrity of the blade by removing excess material, which reduces the risk of the sword breaking or bending during combat. Additionally, the fuller can also produce a distinct whistling sound when the sword is swung, known as the "tachi-kaze," which was believed to have psychological effects on opponents.

It's important to note that not all katanas have fullers, and the presence and design of the fuller can vary across different katana styles and individual swords. Some katanas may have fullers that extend the entire length of the blade, while others may have partial or shorter fullers. The decision to include a fuller and its specific design depends on the preferences of the swordsmith and the intended use of the sword.