Hyō

is a member of Konohagakure's Anbu faction: Root.

Background
In the anime, after the Nine-Tails appeared in the village and began attacking everything in sight, he immediately went to the Hokage Residence to notify the Third Hokage. When he arrived, he alerted Hiruzen of the situation which he was alredy aware of. After saying he would suppress the Nine-Tails, Hiruzen instructed Hyō and the other Anbu to protect the villagers to which he agrees and immediately departs before Danzō arrived.

Personality
Like most Root members, he's still loyal to Root's founder Danzō Shimura and is apparently trustworthy enough to be given the task of delivering top-secret information for him.

Abilities
Although Hyō hasn't displayed any techniques, he is able to sneak up on Sai without being noticed until he strikes, implying that his stealth is on a high level. Like all members of Root, Hyō carries a tipless tantō, which he seems to be skilled with. He is very aware of his surroundings and knows when someone is spying on him.

Tenchi Bridge Reconnaissance Mission
Hyō infiltrated Sai's home and pulls his tantō on him. He handed Sai a letter containing info on his real mission, reminding Sai about the will and purpose of Root. While they were talking, Hyō felt a presence hiding outside and threw a kunai only to find that it was the cat who scrambled off scared.

Trivia

 * Considering the age Hyō is given in the third databook, his anime appearance during the Nine-Tails' Attack on Konoha is not logical as he wouldn't be older than five or six years at that time. This gives us reason to assume that that Hyō was a different individual.