Sunset is the opposite of Sunrise, Amaterasu and Chibiterasu's trademark brushstroke. It does the exact opposite of Sunrise, completely blotting out the sun instead of bringing it out. It is used by Dark Chibiterasu in Ōkamiden. A version of it is also used by Yami in Ōkami, which removes all of Amaterasu's ink pots as well as grant him invincibility.
Both can be countered with Sunrise, and it will also stun the boss in question.