Mao is the new waitress of Onami's restaurant in the Boss Luffy Historical Arc filler episodes.
Mao Kobayashi posing with Mayumi Tanaka (Luffy's VA)
Mao is a character that was added for the anime One Piece for the purposes of a cameo in "Boss Luffy Historical Arc". She appears only in One Piece episode #406-407. She is based on Japanese actress Mao Kobayashi, and she provided the voice.
Like with all the women in this filler arc series. Everyone in the cast refers to her as "Omao".
In Grand Jipang, Mao is Nami's latest hire at her Pinwheel Eatery. She's a kindly girl an hard worker. Friendly to Boss Luffy, but tends to treat him too well for Nami's.
Mao was rather entertained when Usopp brought in a living skeleton he rescued. He was quite the eater and rather rude with his bleaching. he introduced himself as Brook. She passed the bill for the meal onto Usopp.
On the night before the Great Portable Shrine Race, Nami sent Mao over to Franky's workshop with some bento meals. This was out of gratitude, since he was building the Pinwheel Eatery's portable shrine. While there a Perona of the Thriller Company, a rival in the race, attacked, and caused the portable shrine Franky was building to be destroyed and injured Franky and his workers, Mozu and Kiwi. Mao ran off to get help, but he was set upon by zombies of the Thriller Comapny on the bridge. Boss Luffy appeared just in time to blast the pair of zombies away, and she led them all to Franky's workshop.