Ninju

Ninju (ムキムキ), also referred to as Shino Buff Mice, are intelligent mice that work for Tengen Uzui.

Overview
The mice are specially trained for the purpose of being assistants to Tengen and his acquaintances, as seen during the events at Yoshiwara, Tokyo. They are strong enough to carry one sword per mouse, and are capable of navigating small spaces humans normally wouldn't be able to.

Appearance
The mice have pointed snouts and large rounded pink ears. Their fur is mostly grey, but the parts covering their legs and hands are black. Unlike regular mice, the Ninju have extraordinary large muscles. Like their owner, they wear a headband of pale grey that's decorated by three big light pink gemstones arranged in a line.

Trivia

 * In the anime, the Ninju were voiced by Subaru Kimura for Japanese, and Khoi Dao and Bill Rogers for English.