The proper Japanese name for "Ratlings." Small, furry half-human, half-rats.
In Rokugan, these creatures live in the Shadowlands but somehow manage to avoid being tainted. They live in a simple, tribal culture. Their main concern is surviving in that very hostile environment. They look at humans with curiousity, but not with the same sort of fascination that the goblins have. In the time between the Hidden Emporer story arc and The Four Winds story arc, they have managed to not only prove themselves to the Crab clan, but also perhaps to the rest of Rokugan.
In the L5R CCG, these cards are powerful in the right deck. The nezumi trait is marked with Ratling on the card. They now have their own stronghold, The Warrens of the Nezumi.