The series' protagonist. Mamori is an innocent and naive sixteen-year-old girl who, at a young age, overheard her parents talking about her illness. However, she didn't think much of it until she was abducted and sent to Mermaid island, where she became Mirei's partner. She is often made fun of because her surname is written with the same kanji for "virgin" (処女, shojo). She is an Extar whose transformation is a large curved sword, though she later gains the power to transform into a double-bladed spear through the Valkyrie Effect. Unknown to herself, her power level is far greater than Mermaid's other inhabitants; as such, and with her compatibility with Mirei, she is able to unleash the Valkyrie Effect, the ultimate manifestation of the Armed Virus' powers which can manipulate—or even cancel—its effects in other carriers.
Mirei Shikishima (敷島 魅零, Shikishima Mirei)
Voiced by: Yuka Iguchi (Japanese); Morgan Garrett (English)
An observant and intelligent Liberator who becomes Mamori's partner after arriving on the island with her. She doesn't speak much but is very protective of Mamori and is shown to be very powerful. Despite having a mature appearance, she is actually a year younger than Mamori. She is a former Soldier (code name C7), a member of an experimental military unit which tested Mirei and her partner's A Virus powers for warfare applications. As a result, Mirei's body contains a special ability known as Enhance, implanted nano-cybernetics which grant her enhanced strength but causes a great deal of stress on her body. Because of her unwillingness to kill a defenseless enemy, Mirei was set to be terminated, but was saved by one of the scientists who gave her her enhancement. Driven into isolation, Mirei found in Mamori a new reason to live.
Meifon Sakura (櫻 美鳳, Sakura Meifon)
Voiced by: Yurika Kubo (Japanese); Brittney Karbowski (English)
A crafty girl who speaks Kansai dialect and is often seen wearing a partial cowboy outfit. She acts as a double agent, technically being a resident of Veste while sneaking goods to deliver to the girls residing in Atelier Torino. She often holds bets and scams in order to make money which she can use to activate her Extar ability in the form of a golden mech suit. However, the use of her power consumes both the money and her clothes, leaving her in the nude when her power shuts off.
She is known as Meifeng Sakura in the Funimation dub.
Akira Hiragi (柊 晶, Hīragi Akira)
Voiced by: Yuna Yoshino (Japanese); Janelle Lutz (English)
The benevolent Governor of Mermaid, and the founder of Wärter (German for "keeper(s)"), the island's peace-keeping force. While believed by everyone on the island to be the only male resident on Mermaid, she is actually a woman asked by her mother to act like a man in order to stay safe. For physical protection, her mother also provided her with an artificial Extar named Sri. Only Torino and Mirei knew her true gender until she was exposed by Momoka.
Charlotte Scharsen (シャルロット・シャルゼン, Sharurotto Sharuzen)
Voiced by: Asami Seto (Japanese); Monica Rial (English)
The series' first antagonist, a member of Wärter who is cruel and violent. She has a harem of Extars—called the Adel ("nobility")—that she uses all at once when fighting her opponents. She strives to bring Mermaid under her thumb, but is later used as a willing puppet Governor by Momoka.
Kasumi Shigure (時雨 霞, Shigure Kasumi)
Voiced by: Masumi Tazawa (Japanese); Roseanne Palmer (English)
The Commandeur ("commander") of Wärter who is opposed to Charlotte's despotic regime over Mermaid's residents. She started fighting without using an Arm as her partner, Hibiki, had been left in shock following an assault by a girl gang shortly upon their arrival on the island. Rescued by Akira, she was appointed as the commander of the newly founded Wärter to restore order on Mermaid.
Hibiki Kenjo (見城 ひびき, Kenjo Hibiki)
Voiced by: Ayaka Suwa (Japanese); Alexis Tipton (English)
Kasumi's girlfriend and partner. She has been so traumatized by her experience at Mermaid that she refused to leave her room. She decided to join the fight at the very end with the purpose of not letting anyone else suffer the same way she did, apologizing to Kasumi for leaving her fight alone the whole time.
Rain Hasumi (蓮実 レイン, Hasumi Rein)
Voiced by: Saori Ōnishi (Japanese); Tia Ballard (English)
A mysterious woman who together with her lover Lady J forms the duo Lady Lady. Like Mirei and Momoka, they are revealed to be A Virus carriers formerly used by the government who served as Nafrece spies instead as Soldiers, but eventually deserted. As a hybrid of Liberator and Extar, she is able to transform into a powerful beam cannon with variable settings which can, among other effects, disrupt an Extar's powers.
Lady J (レディー・Ｊ, Redī J)
Voiced by: Azumi Asakura (Japanese); Jamie Marchi (English)
Rain's lover and partner who is also an Extar and Liberator hybrid. She is able to transform into a motorbike without her partner's aid. When both girls' Extar forms are combined, they turn into a powerful jet.
Momoka Sagara (相良 百華, Sagara Momoka)
Voiced by: Hitomi Harada (Japanese); Jad Saxton (English)
The series' second main antagonist. Like Mirei, she is a Soldier (code name A3) and her former partner. She is sent to Mermaid alongside her allies in order to locate the source of the Valkyrie Effect. She also harbors a deep hatred of Mirei for "abandoning" her, which turned her into a homicidal maniac, and has volunteered herself for further enhancement; they enable her to transform her chosen Extar into any weapon of her choice and absorb A Virus carriers to enhance her Arm's power.
Torino Kazami (風巳 とりの, Kazami Torino)
Voiced by: Kikuko Inoue (Japanese); Cynthia Cranz (English)
A kind-hearted woman who runs Atelier Torino, a town for girls who either do not want to or are unable to stay at Veste. In the final episode, she is exposed as the government-appointed Observer of Mermaid island.
Nimi Minimi (未弐身 にみ, Minimi Nimi)
Voiced by: Minami Takahashi (Japanese); Bryn Apprill (English)
An Extar who is partners with her girlfriend Noe. Rather than take the shape of a weapon, her Arm form causes her to grow to gigantic sizes.
Noe Ōya (大屋乃絵, Ōya Noe)
Voiced by: Rie Takahashi (Japanese); Skyler McIntosh (English)
Nimi's girlfriend who gets arrested by the Wärter after Nimi runs away, as they were believed to be incompatible.
D5 and E9 (あんｄ 絵, D5 and E9)
Voiced by: Asami Shimoda (Japanese); Carli Mosier (English) (D5)
Voiced by: Marika Kōno (Japanese); Leah Clark (English) (E9)
Like Momoka, D5 and E9 are Soldiers who have infiltrated Mermaid's Wärter until Momoka was sent to the island.
Sri (シュリ, Shri)
An Artificial Extar, a combination of the A Virus and cloned human tissue specifically bred for military combat, which was given to Akira Hiragi by her mother for her protection.
