Contrary to popular belief, traditional Japanese swords, including samurai swords such as the katana, generally do not have blood grooves. The term "blood groove" refers to the groove or fuller found on some Western-style swords. The purpose of a blood groove, as mentioned earlier, is a matter of debate, but it is not a feature commonly seen in Japanese swordmaking.

Japanese swords, including the katana, are known for their curved, single-edged blades and are typically characterized by a smooth, uninterrupted surface without grooves or fullers running along the blade's length. The absence of blood grooves on Japanese swords is due to differences in construction techniques and design philosophies between Western and Japanese swordmaking traditions.

The absence of blood grooves on Japanese swords does not diminish their functionality or effectiveness. The focus of Japanese swordmaking lies in the meticulous forging, differential hardening, and tempering processes that create a durable, sharp, and resilient blade. The resulting hamon (wave-like pattern) and the overall craftsmanship are more significant markers of a traditional Japanese sword's quality and authenticity.

While blood grooves are not found on traditional Japanese swords, it's important to note that there can be exceptions or variations in sword designs throughout history or in modern reproductions. Some modern interpretations or artistic adaptations of Japanese swords may incorporate elements inspired by Western sword designs, including the inclusion of blood grooves. However, this is not a traditional feature of the katana or other traditional Japanese swords.