The Kakushi are a brigade responsible for different tasks pertaining to providing support for the Demon Slayers, which include:

Providing first aid to Demon Slayers on the battlefield.
Cleaning up the battlefield after battles.[1]
Guiding the wounded and injured Demon Slayers to the Butterfly Mansion for further recovery.
Serving as attendants of the Butterfly Mansion, where they provide aid to the manor's residents and those healing on the premises.
Sewing and repairing the uniforms Demon Slay