Zō

There have been several appearances of an unnamed ANBU captain from Konohagakure, wearing white robes and a cat-like mask. It is unknown if any of these appearance are the same person, but there are at least two of them, as the second to appear died shortly afterward.

Invasion of Konoha
The ANBU captain and seven other ANBU members were stationed in the Chunin exam arena during the final rounds of the Chunin exam. When Orochimaru launched the Invasion of Konoha, the ANBU captain and his team rushed to help the Third Hokage. However, before they could reach him, the Sound Four put up a barrier and when one of the ANBU touched it, he burst into flames and died, leaving the ANBU captain unable to assist. He and his remaining men were forced to watch the battle between the Third and Orochimaru. In the end, the Third Hokage died due to using the Dead Demon Consuming Seal and Orochimaru stabbing him with the Kusanagi Sword: Long Sword of the Heavens. When Orochimaru retreated, the ANBU captain and his men tried to prevent them from escaping, but Kidomaru prevented them from following with his webs. At the Third Hokage's funeral, the Captain cursed at his inability to help the Hokage, saying "In the end, all we could do was watch".

The Return of Genno
In the Genno filler arc, a similar-looking ANBU captain and his team interrogated Naruto about Genno by using the Time Reversal Technique.

Three-Tails Arrival arc
A similar-looking ANBU captain died at the hands of Kabuto on a mission trying to find the location of one of Orochimaru's hideouts. He then destroyed his body shortly after sending a bird carrier back to Konoha with information about his mission.

Invasion of Pain arc
Another identically dressed ANBU captain stayed by Tsunade's side during the beginning of the arc, and later accompanied Ino when she went to aid her father and Ibiki Morino. This ANBU captain defeated one of Pain's summons using Lightning Release: Four Pillar Bind with the aid of two other unnamed ANBU.

Trivia

 * This ANBU captain has been given the name Otomatsu by fans. He has also been called Raido, possibly because he was confused with Raido Namiashi.