Mozu and Kiwi

Mozu (モズ, Mozu) and Kiwi (キウィ, Kiwi), also known as the Square Sisters (スクエアシスターズ, Sukuea Shisutāzu) due to their square-like hairstyle, are very loyal to Franky, and go with him everywhere. Mozu is the sister with the yellow bikini top, yellow slacks, and straight edged hair, while Kiwi is the sister with the red top, red bikini bottom, and curly edged hair. They have a tendency to mimic his reactions. They often walk sideways in high winds, due to the fact that otherwise their hairstyles would cause them to be blown back. During battles, they fight with samurai swords. They are accomplished swordswomen but are not especially powerful (average instead of superhuman), as Franky and Kalifa easily subdued them. They both also have a tendency to add "Waina" to all their sentences. They've done that ever since they were young.

Past
The earliest history of the two girls was that they were seen riding the Puffing Tom on its opening day are them when they were kids. They were inspired by this event and tried to be shipwrights. They however failed the Galley-La company tests and began drinking heavily. They were then found by Franky and started working for him after he encouraged them to stop.

Water 7 Arc
When CP9 invades their hideout, they are knocked down and out by Kalifa for not letting them in. Later when the Straw Hats chase after the sea train, Puffing Tom, with the Rocketman. Mozu and Kiwi along with the rest of the Franky family, accompany them to the government headquarters, Enies Lobby, as Franky was captured by CP9. Once there they help hold off the naval marines to allow the Straw Hats go on ahead and try to rescue Franky and Nico Robin. They were also specifically responsible for opening the gates to the center of Enies Lobby for the Straw Hats. They were blown into the Enies Lobby waterfall by cannon fire, but survived thanks to the giants and Paulie.

Post Enies Lobby Arc
They appear again in the Post Enies Lobby arc to see Franky off, and are horrified when Nico Robin attempts to force him to join by squeezing his testicles, claiming that they will fall off like a piece of fruit from a tree.

Cameos and Crossovers

 * The Square Sisters appeared in the game Jump Ultimate Stars for the DS.

Trivia

 * In the 4th Japanese Fan Poll, Kiwi and Mozu are both ranked as the 122nd most popular characters in One Piece.
 * Oda seems to enjoy naming women after birds, and this trend continues with the Square Sisters, Kiwi is named after the Kiwi, Mozu is named after the Bull-headed shrike (Lanius bucephalus), or in Japanese, Mozu.