Nioi-ashi (匂足) is a term used in the context of Japanese swords. It refers to a pattern where the ""Ashi"" - the line or dot that appears from the blade edge towards the tip - is composed of ""Nioi"" (?), the whitish misty appearance along the cutting edge, which is a more subtle hardening compared to ""Nie"" (?), the visible particles of hardened steel.

The term ""Nioi-ashi"" translates to ""scent foot"" in English. It is named so because the pattern appears as a long, rod-like shape extending from the blade edge (Habuchi) towards the blade tip, and it is composed of ""Nioi"".

Depending on the shape of the ""Nioi-ashi"", it can be further classified into different types such as ""Koashi"" (small foot), ""Sakaashi"" (reverse foot), and ""Nezumiashi"" (mouse foot).

Therefore, ""Nioi-ashi"" adds a unique and interesting visual effect to the blade, enhancing its overall aesthetics and value.