Mei is the most recent Kage of the Hidden Mist Village and had a rivalry with Tsunade.
She makes her first appearance after being requested to the Kage summit by the Raikage to discuss the problem of Akatsuki. She was accompanied with her bodyguards Ao and Chojiro. She acts motherly to the teenage Chojiro and defends him from the older Ao whom is a little hard on Chojiro. She also sometimes misunderstands things Ao says, believing him to be mocking her, and threatens him.
At the Kage summit, it's revealed that the former Mizukage, Yagura theJinchuuriki, was being controlled by someone and that Akatsuki was created in the Hidden Mist, and it's possible that the two events are related. It was also suggested that she could not lead the Kage alliance because there may be those loyal to Akatsuki inside of the Hidden Mist.
When the white half of Zetsu barged in and revealed that Sasuke was there, she scolded Raikage for killing him and said that they could had interrogated him. Later when Sasuke appeared to attack Danzo, the moderator of the summit, Mifune, clashed swords with Sasuke while Danzo took the opportunity to escape along with his bodyguards. Ao pursued Danzo and Mei prevented Sasuke's from chasing after. Chojiro then knocked Sasuke into the outer hallway and Mei used her jutsus to seal the doorways, trapping Sasuke in with her. She revealed that she has 3 affinities: earth, fire, and water. Because of this she has 2 Kekkei Genkais: lava and boil. She used her lava to block the doors, and she used her Boil to create an acidic mist that ate through Sasuke's Susanoo. However Sasuke was saved by white Zetsu whom managed to surprise all of the Kage's and their bodyguards with a jutsu. After dealing with Zetsu, she stopped her jutsu since Sasuke broke a hole in the wall leading to everyone and she didn't want to hurt them.
After this, Madara appeared and saved Sasuke. He then decided to tell them his plan: he wanted Sasuke to weaken the Kages so that he could keep them prisoner so they couldn't try to stop him, but Sasuke failed. However he offered them a chance to side with him. after hearing his plan. He's going to combine all of the Bijuu and become a Jinchuuriki, and then use an infinite Tsukiyomi to unify the world. The Kages thought he was crazy and refused to hand over Naruto and Killer Bee, so Madara declared world war.
Danzo and his bodyguards, Fu and Torune, were aware that Ao was tailing them and Fu set a trap. Fu switched his mind into a puppet and when Ao passed by Fu attacked and traded bodies with Ao, trapping him in the puppet while Fu tried to remove Ao's Byakugan, but the seals Ao wore as earings prevented this. Fu decided to chop off Ao's head and then come back for it later, but was stopped by Mei. Fu pretended to be Ao and thanked her for saving him, saying that one of Danzo's bodyguards are from the Yamanaka clan and that he couldn't control his body. Mei asked if he wanted her to undo the seals on the Byakugan and he accepted, but this was a trick and she realized that Fu was still in control of Ao's body so he went back to his own body before she could hit him with Chojiro's sword. But this was a bluff and she only struck with the flat side of the sword, which still hurt Ao whom returned to his body.
Though the full extent of her abilities have yet to be shown....Mei is a kage ranked ninja despite her youthful age and is no doubt a formidable combatant. So far Mei has shown to be able to use the nature types of fire, water and earth. With this Mei has combined at least two sets to form two kekkei genkai nature types. Something considered rare. She has also shown to be very smart, blocking all possible exits for her fight with Sasuke.
Boil Release Combining water and fire nature chakras, Mei can create boil release. A nature
Mei Terumi Using Boil Release In The Anime
on one combat, were allies aren't around as they to risk the people being attacked. Though Mei has stated she can alter it's acidic qualities or the pH of the gases, and no matter how acidic the gases get the user or Mei doesn't seem to be affected by it at all.
Lava Release The second of Mei's kekkei genkai's. This nature type combines the elements of earth and fire. When using this technique, Mei will release the lava from her
Mei Terumi Uses Lava Release Techniques
mouth upwards, allowing it to fall upon her targets. This attack spans a wide area, making it difficult to avoid. Using lava release, Mei can release many blobs of lava that will quickly solidify, around door ways or holes in walls, sealing of any exits that her opponent may intend to use. This attack can be both offensive and supplementary in various scenarios.