Pein is a muscular red-orange tom with purple ringed eyesand several piercings along his nose, with 2 under his mouth.
Pein is first seen watching Kakashi, and several other cats fight. Later, he is involved in the fight, wanting to watch their skills.
A few days later, he is seen with several other cats. He comments on several things, and is forced to insert his place as leader several times.
He, Deidara, and Konan later talk about how they could fireproof Konan's paper in an atempt to ruin the changes of Ichigo getting out of her attacks. He suggests they use a mix of water, wax, and chakra to fix it. Deidara suggests using water, wax, and leaves or bark. Each one makes their own mixture. The bark one was the one that caught fire fastest, while the leaves smoldered and then burst into flames. In the end, the chakra-infused mixture worked best.
Pein is a calm, serious, aloof, and detached cat. He had traumas as a kit that had enlightened him to the true meaning of pain and suffering. He sought to show the world the meaning of pain by using an ultimate weapon to deter future wars, by means similar to "mutually assured destruction", and showed no moral qualms about his actions. Nonetheless, he was seen to be quite respectful, particularly to the fallen and the dead. Given the groups members' frequent bickering, he often quelled them and encouraged better relations among members. He is quite sensative when talking about "pain".