Kagerō

was a jōnin of the Fūma clan. She was among the Fūma clan members who were deceived by Orochimaru. She was also one of a three-member group (alongside Jigumo and Kamikiri) who guarded Orochimaru's base in the Land of Sound.

Background
After the Fūma clan finished a war with a neighbouring country, they wandered the Land of Rice Fields hoping to settle down. Near the end of their journey, Orochimaru and Kimimaro appeared before the Fūma and told them that if they joined Otogakure that Orochimaru would help in restoring their power. Kagerō agreed and left with them.

Personality
She showed extensive loyalty and dedication to her fellow clan members, using her Ephemeral Vengeance even though it would endanger her life. This same respect was also shown towards Orochimaru, who Kagerō viewed as the person who will bring the Fūma clan back into its glory. She knew of Sasame's bond with Arashi, and Sasame showed her considerable respect, addressing her with the -sama honorific. She constantly made references to the life of a mayfly while in her male disguise, which makes sense, as "Kagerō" can mean "mayfly". Kagerō also shows deep appreciation for poetry as when in her male disguise she recited a short poem comparing herself to the mayfly before attempting to sink Naruto using the Earth Release: Antlion Technique

Abilities
Though she was actually a young girl, Kagerō constantly disguised herself as a grotesque, hunchbacked man with buck teeth. This transformation can't be dispelled even if she was wounded. 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 was able to use Antlion Ninja Arts: Ephemeral, creating four wings out of chakra on her back. She could then fire a gigantic blast of chakra at her opponent: the amount is said to be so great that this jutsu could only be used once in a lifetime. She could also fly and teleport while in this form.

Kagerō could also use a Fire Release technique that releases a flammable gas and could access a Fūma clan technique that connects the user's and the target's hearts with chakra threads and makes them beat at the same rate - when one speeds up, slows down or stops, the other will as well, meaning that if the user dies, so will the victim.

Land of Rice Fields Investigation Mission
Kagerō, along with Kamikiri and Jigumo, attacked Naruto Uzumaki and Sakura Haruno when they were hiding in a temple with Sasame. She then used the Antlion technique to suck Naruto into the ground. Gama, Jiraiya's toad, used his tongue to pull Naruto out of Kagerō's pit, which Naruto took advantage of by wounding Kagerō with his Rasengan, causing her to retreat.

Though she was wounded by the Rasengan, Kagerō showed up at the second battle after Sasame drugged the Leaf ninja's drinks. She told Sasame that if she helped them capture the Leaf ninja, they would take her to see Arashi. However, Sasame realised that Kagerō and the others were actually planning to kill Naruto and the other Leaf ninja. The Leaf ninja had discovered the drugs and used substitutions to deceive the evil Fūma and bring them out into the open. During the second battle, Kagerō moulted her male form to use her Ephemeral Vengeance. Jiraiya managed to counter the technique and she escaped with Kamikiri and Jigumo in her arms.

When Jigumo and Kamikiri begged Orochimaru (actually Arashi in disguise) to heal Kagerō, he refused due to their failure to kill the Leaf ninja. After Orochimaru killed them, he did heal Kagerō. Kagerō encountered Sakura in Orochimaru's hideout while posing as Kabuto Yakushi. Kagerō tried to kill Sakura, but once again, Naruto wounded her with the Rasengan. She attempted to kill Naruto by synchronising their heartbeats and stopping hers, but Sakura cut the chakra threads connecting them with a seal obtained from Sasame, therefore freeing Naruto from Kagerō's attack. Kagerō then died after warning Sasame about how much Arashi changed.

Trivia

 * Kagerō can be translated or.
 * The mayfly is a reference to her remarks of how life is ephemeral, similar to a mayfly.
 * The heat haze is a reference to Kagerō's ultimate technique, which has fire-like properties, as well as having a fire-nature technique.

Kagerou Fuuma