Canary

Canary  is an apprentice butler of the Zoldyck Family. Anyone attempting to pass her post on the estate will be expelled via force.

Background
Canary grew up in Meteor City, the city the Mafia and the Phantom Troupe also call home. In the 2011 anime series, she also says that if Killua ever wishes to visit the city one day, she will act as his guide.

When she was 10 years old, she took down within five minutes a Blacklist Hunter together with a hundred of his men attempting to go through her post. She refuses to let Gon pass her post beating him pretty badly, but is later convinced that his intent as Killua's friend is true. She is thereafter knocked out by Kikyo Zoldyck, but stills accompanies Gon to the servants' quarters. Canary is taken hostage by the butlers briefly inside, but is released after Gotoh plays a coin game with Gon.

Canary appears to have a personal relationship with Killua. When Gon first mentions Killua in front of her, he notes that just for a fraction of a second, her eyes convey gentleness or consern, although she tries to supress it. A flashback shows Canary and Killua's first meeting. Killua wishes to become friends with her, but she tells him that, as an employee of the Zoldyck family, she is not expected to have any feelings towards her masters.

Zoldyck Family arc
Canary first appears as a guard on the path to the Zoldyck residence, preventing Gon and friends from reaching Killua. She is shown to greatly overpower Gon in combat with her staff, although the longer he challenges her, the more reluctant she becomes to attack. Eventually, she refuses to attack Gon entirely. Gon tells Canary that she is different from Mike, and that although she made hide her feelings, she still has a heart. It's implied Canary would have let them pass, and begs to Gon, "Save Killua-san" before being knocked unconscious by Kikyo Zoldyck.

Upon recovering, Canary leads Gon, Kurapika, and Leorio to the Intendants' Room, so they can use their phone in hopes of reaching the main residence. During their wait for Killua, Gon and the others are invited to play a game with Gotoh, with Canary's life used as a gamble. However, Gon wins the game, and Canary's life is spared.

New Hunter Chairman Election arc
Canary returns alongside Gotoh as a guardian to Killua, who had just broken Alluka out of the Zoldyck estate. Canary and Gotoh both accompany Killua due to the requirements of the Level 4 Restriction the Zoldyck family placed on him. Killua explains that he requested Canary to come with him so Alluka, who he claims as a girl, could receive delicate care. Canary understands that Killua is counting on her, and as his friend, she states that she would go to the depths of Hell for him.

After being intercepted by Illumi's controlled drivers, the group is forced to go on foot, however Killua uses his Kanmaru ability to lose them. Following this the servants are met by Hisoka whom Gotoh decides to fight in order for Canary, Tsubone and Amane to follow Killua. As Killua increases his speed, Tsubone is forced to turn herself into a motorcyle with the other two riding on her to reach Killua's speed. When Killua jumps into the forest making it impossible for Tsubone to follow, the trio makes it to the airport where the butlers were arranging an airship to travel, they eventually can manage a total of 8 airships with Canary distracting Amane to ensure Killua escapes the survilleance of the butlers although she denies this. Amane becomes frustrated and attempts to follow Killua but Canary tells her that at this point there is really no way to follow after Killua without him suspecting, and upon her rather comical frustration, Canary points out that Amane is cute to which she embarrasses.

Combat
Being an apprentice butler of the Zoldyck family, Canary is an expert fighter. Her weapon is a rod that she always carries with her.

Nen
So far she has not shown any Nen abilities of her own, however as her aura was used by Tsubone in her motorcycle mode, it is implied she knows how to use Nen.

Trivia

 * Canary has a rather large role in the HxH muscial, The Nightmare of Zoldyck, identified as one of Killua's precious friends.
 * Canary's past was never revealed in the manga, but a Hunter x Hunter character guidebook published in 2001 revealed that she originated from Meteor City. In Madhouse's adaptation, a scene is added in which Canary states that she was from Meteor City and she knows how to use the Shadow Step.

Reference

 * 1) Hunter x Hunter Manga volume 05, chapter 041 : Zoldyck Estate Arc
 * 2) Hunter x Hunter Manga chapter 324 : New Chairman Election Arc