is a black cat who reoccurs in the background of the anime and manga. She appears in every episode of the anime and randomly in the manga. Despite her level of recurrence, Kuroneko-sama has had few instances of plot significance, having stopped Wolfwood from cheating in a game of chess during Escape from Pain and when Vash is replaced by Kuroneko during Hang Fire. Nightow has stated that she is just something easy and calming to draw in between action scenes. His most common response to queries as to her nature or significance at anime convention panels is "Kuroneko-sama is a small black cat."

In Trigun Maximum, Kuroneko only appears in Nightow's commentary at the end of each issue, often criticizing the author's lazy and silly nature.

In Trigun Badlands Rumble, Kuroneko can be first seen napping at the news stand where Vash finds out he is blamed for Gasback's bank heist. The cat can be seen again, watching Meryl and Milly as they discus their situation with Cain's statue. Also, during the bar fight later in the film, Kuroneko flies through air along with many other items, seemingly thrown by someone as a projectile.