Adelle Bascùd

Anaguma is a character that appears in the fourth movie, Dead End Adventure. She was an assistant to the boiler man, Biera (whom she calls Grandpa) on board Gasparde's ship. She was thought to be a boy due to her appearance and her masculine voice (which is actually her normal voice).

Once Biera was stricken sick, Anaguma desperately begged Gasparde to help him. Gasparde made a deal with her that if she could kill a pirate, she would be considered his crewmate and he would help her grandpa. She quickly left the ship to do just that and stowed away on the Going Merry thinking it was the weakest ship, though quickly finds out otherwise when she tries to kill Zoro and travels along with the Straw Hat crew during the Dead End Race.

During the race, the Eternal Pose that was supposed to point to their goal (Partia) was revealed to be a fake. Luffy suspects Gasparde, whom he has met and despises, to be the culprit. Anaguma supports him on his claim and asks the crew to help rescue her grandpa, to which all (except Usopp) agrees to. Through Nami's guidance and Chopper's nose, they reach Gasparde's ship. Once there, she tells Biera what she has learned from the Straw Hats: stay alive no matter how bad it gets. Biera stays behind so he could overload the boiler and blow up Gasparde's ship. When she begs the crew to turn back, Zoro knocks her, out revealing her gender to them when her cap falls off.

After Gasparde is defeated, its revealed through her 'grandpa' Biera to Shuraiya Bascùd that he rescued a little girl from a river eight years ago. The girl could only remember her name: Adelle Bascùd; Shuraiya's sister whom he thought was dead. Despite some awkwardness at first, she comes to accept her brother. The Straw Hats manages to get to Partia but are pursued by Marines before they could reach land and claim their prize, leaving Adelle with her brother and 'grandpa' behind. Shuraiya promises to start a new life for them.

Trivia

 * Chopper seems to have known her gender the entire time, which makes sense since he's a doctor.
 * Anaguma, her nickname, means "badger".