Chiaki Tanimura

is a member of Red Tail and the fifth leader, who can use four guns simultaneously.

Appearance
Chiaki is a slim, petite girl with short black hair and a small bust whose expression is often a deadpan. She wears the Ishiyama High School uniform and her skirt ends above the knee, but beneath it are remodeled airsoft guns strapped to her thighs but in the anime, they have become highly pressurized water guns.

Personality
She doesn't speak much, often using hand gestures and nods to express her meaning. Despite her standard expression and tendency to shoot first, ask questions later, she appears to have more of a feminine side than many of her fellow Red Tail members.

She usually refers to girls who make cute faces (happy, innocent, etc.) as "so cute" especially for Aoi. She also tends to shoot men that are hitting on Kunieda except for Oga as she realizes that Kunieda is in love with him.

Nene Ōmori states that when it comes to video games, Tanimura's personality is completely different. As shown when she stated she practiced all night for a video game to prepare herself and to compensate for a previous video game loss.

Tōhōshinki Arc
Chiaki is first introduced along with fellow Red Tail member Aoi and Nene following the girls' return to school. While walking the hallways, a boy dives to the floor in an attempt to see her panties and she shoots at him until Aoi recommends she stop.

She and Nene go to confront Oga soon after about his previous encounter with Aoi, and when they end up badly injured in the infirmary, the incident is blamed on him. In fact, they were beaten up by the MK5 in order to force Oga and Aoi to have a serious fight. Later, she and Nene encounter Furuichi and Oga at a swimming pool, where Furuichi's former upperclassmen unsuccessfully flirt with them.

When the vast majority of the Ishiyama High student body challenges Oga to prevent him from reaching Tōjō, Chiaki is among the Red Tail group who intervenes.

Saint Ishiyama Academy Arc
After the school's demise at the hands of an overpowered Oga, Chiaki and the rest of the Red Tail had to go to school at St. Ishiyama High, in room 3F while their school was being rebuilt. She appears as a support character and takes the outfit of a cheerleader to support the Ishiyama gang during the Six Horsemen vs. the Ishiyama gang volleyball match.

Mobichi Arc
During school, Furuichi is shown to have a cold while he is in his homeroom; Chiaki, who has her own box of tissues present, notices that he also brought his own. Aoi recommends that he goes to the infirmary and is subsequently asked to accompany him, causing Chiaki to mentally remark that he is gross. Later, when Chiaki sees that Lamia has arrived, she begins offering candy to the young girl. Furuichi returns shortly after and casually begins talking to Nene, which Chiaki takes note of. She then looks on as Kanzaki and Himekawa ask Furuichi to step outside with them.

Outside, Chiaki then watches a fight between Furuichi and Kanzaki with Himekawa. Upon seeing that Furuichi has tackle hugged Aoi, Chiaki, who is slightly mortified, refers to him as "trash". Chiaki then looks on as Furuichi defeats both Kanzaki and Himekawa instantaneously, shocking her.

Chiaki later accompanies her fellow Red Tail to the local river, where they are joined up with several of their peers. She stands tall beside her fellow delinquents as they prepare to take down the Shadow Force.

Later, Chiaki sees Lamia acting bossy towards Furuichi and begins gossiping with Yuka about it; moments later, they go to Lamia where Chiaki tells her that Furuichi might ask to see her panties someday. Oga then begins supporting Furuichi by saying that the girls should not call him a lolicon; despite so, Chiaki still looks at him darkly while referring to him as such. However, they are then just told to stop teasing him. To Chiaki's surprise, Nene tells him that they know that he is not a lolicon and turns to Chiaki afterward. Surprised with her leader's response, Chiaki coldly apologizes to Furuichi while still referring to him as "trash" for earlier.

Saint Saint X'mas Arc
During lunch, Chiaki sits with the rest of the Red Tail and listens to Yuka as she explains of the Saint Saint X'mas competition. 

Return to Ishiyama High School
One day, she and the other Red Tail members find Aoi writing fortune cookie messages.

Later in the afternoon, several of the Red Tail, including Chiaki, head to the Kunieda residence where they see an injured Aoi being tended to her wounds by her grandfather. Aoi explains that she is fine, though the ones who attacked her were from Majōgari Academy, apparently led by Ringo Hōjō; upon hearing the name of Aoi's predecessor, an already-anxious Chiaki grows shocked.

A meeting is eventually held outside; among the attendees are the other Red Tail and Tōhōshinki. After several back-and-forth conversations, they all decide to gather information on the "Killer Six Elements" before launching an attack; moreover, a private fight will be held between Yōhei Nasu and Tatsumi Oga. Problems soon arise with Kanzaki's and Himekawa's disapproval of Oga as their leader. It is eventually decided that a game of rock-paper-scissors will decide their alliance's leader and everyone, including Chiaki, participates. The results conclude with Baby Beel being their leader.

The following day, Chiaki and Nene follow Seiji Kameyama of the Poltergeists, where they see that he is buying a drink from a vending machine. Chiaki reports their findings to Kanzaki and Furuichi. During so, she comments on how everything feels very similar to when they all played that video game. After some time, Nene points out an apparent change in the Poltergeist's face, though Chiaki fails to see any difference with his appearance. Suddenly, his face slowly melts away before their very eyes. As Nene and Chiaki begin to comprehend what has happened, both become wide-eyed and mortified as they have seen; however, she eventually gets over this incident.

She eventually regroups with the rest of the Red Tail. When news of the planned battle between Aoi and Ringo reaches them, all of the Red Tail members, including Chiaki, head out to the front lines. Along the way, they are confronted by members of the "Reborn Red Tail", who successfully stop the other group from moving forward. Both generations then clash with one another; unfortunately, all members of the Red Tail are badly beaten and defeated.

They are subsequently taken to a desolate area within the school with Aoi and Ringo inside. Upon their arrival, Ringo proposes that Aoi fight either Nene or Oga for the other's safety or otherwise be beaten along with all of them. Chiaki screams for Aoi to fight back. Still restrained, Chiaki watches as Ringo puts further pressure on Aoi by threatening to burn out one of Oga's eyeballs; Fortunately, Aoi is unaffected by the threat and later makes a triumphant comeback against Ringo. She later proclaims to those present that she will be reclaiming her title as leader of the Red Tail, causing Chiaki to cry with happiness.

Chiaki is then subsequently freed from the "Reborn Red Tail" and she goes over to Yuka, holding her hands as they look back at their old leader. However, their happiness quickly disappears after they see Ringo about to burn one of Oga's eyeballs, as she said she would earlier; despite Chiaki's worries, this ultimately does not occur. Chiaki resumes watching Aoi's fight silently from afar. She later smiles when Aoi is left victorious against Ringo.

Several days later, Chiaki and Yuka go to the tennis courts with several of their classmates. Chiaki silently stands next to Yuka throughout her time there.

Late at night, Chiaki and several of her classmates from Saint Ishiyama Academy head to their high school.

Upon arriving, they are approached by the members of the Himekawa Special Forces, surprising Chiaki. She then engages in combat against the entire force; however, after fighting for a certain amount of time, she is utterly defeated by them all. Chiaki lies limply near the bushes against the wall to one of the campus buildings.

Chiaki eventually recovers enough to go home by morning, where she cleans her bruises and changes into casual attire. However, she is unable to go sleep due to "Brainless Furuichi" being present, a sight that leaves Chiaki speechless. Instead, she sits next to a table that he is standing on while he tries to sweet-talk her. Eventually, Chiaki's siblings find her and see "Brainless Furuichi" whom they mistake for a talking toy; she lets them play with him and watches from their balcony as the two boys' experiment nearly kill "Brainless Furuichi".

Later, Chiaki gets a phone call from Aoi who asks him whether she has seen Furuichi anywhere near her; Chiaki casually tells her Red Tail leader that he came to her house but eventually left a while ago. 

Powers & Abilities
Though showing minimal physical strength, Tanimura has dual modified airguns which she keeps strapped to her thighs. Though she is rarely shown using them, she is an expert marksman. On a side note, she has unexpected experience in video gaming. She reveals she has a younger brother who usually asks her to play with him during two player games.

Techniques

 * Simultaneous barrage: Tanimura reveals she keeps more than two guns with her. She possesses the incredible ability to use four guns almost all at once. After firing the dual guns she currently wields, she tosses both guns into the air while quickly grabbing the other two she has and repeating the process. In the anime, the technique is further elaborated when she uses this ability the first (and so far the only) time during the Ishiyama assault against the MK5.

Nene Ōmori
It seems that Nene Oomori and Chiaki are close friends. As shown when they when to the public pool together, or when they follow Seiji Kameyama of the Poltergeist together. When Chiaki, Nene, and the others play net games to gather information from Prince En, Hajime Kanzaki asked to change pairs, so Chiaki can pair up with Nene due to Nene being bad at playing Video Games. Chiaki said that Nene is adorable and cute when she gives up.

Aoi Kunieda
Chiaki and Aoi are close friends. She respects her as a very good and protective leader. In fact, Chiaki is first who found out that Aoi fell in love with Oga.

Quotes

 * "Kawaii": for Aoi Kunieda.
 * "Another shake, please."
 * "Cool."
 * "Can I play this?": requesting if she could play Street King of Fighters IV.
 * "That's a big Love Letter..."
 * "That's a big font..."

Etymology

 * The name Chiaki means "thousand" (千) (chi) and "autumn" (秋) (aki).
 * Chiaki's surname Tanimura means "valley" (谷) (tani) and "town, village" (村) (mura).

Trivia

 * In the anime, Tanimura's modified air guns have been changed to highly pressurized water guns.
 * Of all the Red Tail members featured, Tanimura is the only member shown to use a projectile weapon.