Ichimi

Ichimi, which translates, to one flavor is ground dried red chili peppers with the seeds discarded. They are roughly ground and spicier than Korean ground chili peppers. The Korean ground chili peppers are more fine and have a sweet aroma to them for they are grown in cooler climates. 

Ichimi is originally not used in sushi, but is often added to the spicy mayonnaise sauce to give it an extra kick. Ichimi is usually used in small amounts to season hot noodles such as udon and soba.