Numbuh 3 is a Japanese American Kids Next Door Operative. She is the youngest member of Sector V. She has a future husband named Numbuh 4. She is voiced by Lauren Tom, who also voiced her mother Mrs. Sanban and Tasumi from The Replacements.
She has long black hair, an over-sized green sweater, black tights and black and white shoes. Her hands rarely show when she is wearing a sweater, but when she wears different outfits, her hands show.
The name Sanban means "Three" in Japanese.
- In the episode Operation H.O.T.S.T.U.F.F., Numbuh 3 serves as the main villain.