Chachamaru

Chachamaru is a small tricolor calico cat, mostly white with patches of black and brown and a pair of large amber eyes.

Strapped to its back is a brown box fitted with a syringe, built by Tamayo to gather demons' blood. A red collar around its neck holds a paper talisman made by Yushiro, which lets the cat conceal itself using his Blood Demon Art.

Little is revealed about the cat beyond its role as Tamayo's familiar and courier for her studies. Its discipline suggests it has aided Tamayo and Yushiro for a long while.

Like many cats, Chachamaru enjoys affection and will pause briefly to be petted before returning to its task. After its transformation, it is said to have accepted its new state contentedly out of love for Tamayo.

Chachamaru first appears after Tanjiro's clash with the former Lower Moon demon Kyogai, arriving invisibly until it meows to reveal itself, then vanishing again once the blood is stored. It returns to collect samples after later battles and at one point delivers a note from Tamayo hinting that Nezuko may be able to withstand sunlight.

In readiness for the final battle, Tamayo turns Chachamaru into a demon, a choice that troubles her deeply, motivated chiefly by her wish that Yushiro not be left alone. During the fight against Muzan, the cat is cut to pieces while administering an antidote to the wounded Hashira, but Yushiro later finds it and reassembles it, since its new demon body can survive being dismembered.