Kagerō

Kagero is a member of the Fūma clan at the rank of Jonin. She was among the Fuma clan members who were betrayed by Orochimaru. She was one of a three-member group (alongside Jigumo Fuma and Kamikiri Fuma) who guarded Orochimaru's base in the Land of Rice Fields.

Though she was actually a young girl, she constantly disguised herself as a member of the opposite gender (mostly a grotesque, hunchbacked man with buck teeth). She shows extensive loyalty and dedication to her fellow clan members, using her Ephemeral Vengeance even though it would endanger her life. This same respect is also shown towards Orochimaru, who Kagero views as the person who will bring the Fuma clan back into its glory. She knows of Sasame's bond with Arashi, and Sasame shows her considerable respect, addressing her as "Kagero-sama."

She constantly made references to the life of a mayfly while in her first male disguise, which makes sense, as "Kagero" can mean Mayfly.

Plot overview
Kagero, along with Kamikiri and Jigumo, attacks Naruto Uzumaki and Sakura Haruno when they hide in a temple with Sasame. Though he/she was wounded by Naruto Uzumaki's Rasengan, Kagero showed up at the second battle and shaded her male form to use her Ephemeral Vengeance. Jiraiya managed to counter that and she escaped with Kamikiri and Jigumo in her arms.

When Jigumo and Kamikiri begged Orochimaru to heal Kagero. As Jigumo and Kamikiri are killed, Orochimaru did heal Kagero. Kagero encountered Sakura Haruno in Orochimaru's hideout while posing as Kabuto Yakushi. Kagero tried to kill Sakura, but Naruto wounded her again with Rasengan. She attempted to kill Naruto by synchronizing their heartbeats and stopping hers, but Sasame cut the chakra threads connecting them, and died after warning Sasame about how much Arashi changed.

Abilities
While disguised as a man, she would use the Earth Release: Antlion Technique to cause everything in a certain area to be drawn into a large pit. After removing this form, she is able to use Ephemeral Vengeance, creating four wings out of chakra on her back. She can then fire a gigantic blast of chakra at her opponent: the amount is said to be so great that this jutsu can only be used once in a lifetime. She can also fly and teleport while in this form. Kagero can also use a fire technique that releases a flammable gas and can access a Fuma clan jutsu that connects the user's and the target's hearts with chakra strings and makes them beat at the same rate- when one speeds up, slows down or stops, the other will- meaning that if the user dies, so will the victim. She also possesses- or was subject to- a transformation jutsu that is not dispelled when the user is wounded.