Ink Mouse

Sai creates a swarm of mice made from his Super Beast Imitating Drawing. Sai uses the mice to search for a target much faster than the he would be able to on his own. Being so small, the mice are inconspicuous, also making them suitable for covert message delivery.

Trivia

 * While unnamed in the manga and anime, it was named in the Naruto Collectible Card Game.