Abi

Abi is a little girl from Water 7. She sought help from Luffy during the first filler episode after the Enies Lobby events in the anime.

History
Prior to the events when the Aqua Laguna hit Water 7, Abi and her family sought shelter from approaching tidal wave. As usual, they couldn't bring the family Yagara Bull, Aobire, along with them. However upon returning home, it was discovered that Aobire had gone missing. Since then Abi desperately searched for her beloved pet. With her experiencing recurring dreams about Aobire calling out to her, Abi was ever more determined. Three days later, Abi caught sight of Luffy roaming around the streets along with Chopper. Seeing as he and his crew were the ones who saved Iceburg, Abi decided to ask Luffy for help.

With her money that she kept in a Yagara Bull piggy bank, Abi asked Luffy to help her search for Aobire. Luffy accepted and together with Chopper, they began searching all over Water 7. Despite searching everywhere however, the three couldn't find Aobire, even with help from Robin's Devil Fruit powers. Eventually Abi and company learned from another Yagara Bull, through Chopper, that Aobire was last heard on the night when the Aqua Laguna hit. Just as it seemed hopeless, Luffy luckily found a piece of Aobire's muffler.

Following another piece of the muffler, Abi and her two Straw Hat companions eventually came to the underground passages of the town that was built over by present day Water 7. As the three ventured through the forgotten town, they eventually came to a room mostly filled with water. There Abi found Aobire and asked him to come with her. The old Yagara Bull, through Chopper's translation, however refused her offer and told Abi that it wasn't possible. Not understanding why, Abi rushed towards her old friend. It was then discovered that Aobire was now a ghost when Luffy tried to grab the Yagara Bull. Seeing as nothing else could be done, Luffy then grabbed Abi before she could reach the specter as it began to disappear.

After Aobire's ghost disappeared, Abi and company found a baby Yagara Bull hidden amongst the debris nearby. The baby was clothed with Aobire's muffler. It was then discovered what had happened to Aobire during the Aqua Laguna. The old Yagara Bull had heard the cries of the baby and came out of the storm to rescue it. He found the baby and protected it from the cold with his muffler. However he had died in the process. With this new information, Abi decided to take care of the baby. With the happy baby in hand, Abi decided to reward Luffy for helping her find Aobire and fulfill his last wish. Luffy on the other hand, decided to not take the reward and instead gave it back to Abi in order to help the baby grow up healthy.