Aiko had wavy mid-back length dark brown hair that is half pulled back by a light blue rectangular hair clip where she does not have bangs except for what escapes her hair style and burgundy colored eyes with visible lower eyelashes.
Her JIDA uniform consisted of a long-sleeved black tailcoat with two rows of gold buttons on the front, light green details including the shoulder epaulettes which had a Sam Browne belt passing diagonally over her right shoulder. She wore a pair of white gloves along with an armband on her left arm, and a white web belt with with a gold waist-plate. She also wore the standard black skirt, dark gray pantyhose and knee-high black boots.
Aiko was a focused soldier who cares deeply about her comrades. When she reported their deaths, she cried. Even so, she was serious and hard-working, willing to continue with dangerous missions even after such loss. She did not hesitate to sacrifice herself in order for her comrades to escape.
Aiko was brave, selfless, and compassionate. A notable example is when following her whole team's massacre, she gave a red herring to the vampires about where the humans were, intending to buy them some more time, staying loyal to her comrades to the end.
She thought and acted quickly. In order to protect information about their comrades, she ordered her injured team to commit suicide when vampires surround them.
At some point of Aiko's life, she joined the Japanese Imperial Demon Army. Then later, the Moon Demon Company. Eventually, Aiko was promoted to the rank of sergeant.
Events of 2020
Aiko is first seen observing the practice fight at Ebina rest stop where she says to a comrade that the fight must be the punishment for Shinoa Squad's late arrival. After, she remarks that they are useless without team work.
During the attack against Nagoya, Aiko leads a fifteen member team to assassinate a noble vampire. Although they succeed, they suffer eight casualties and the remaining seven have injuries but can still walk.
She arrives at the regrouping point after Shinoa Squad and Narumi Squad. When she asks about them coming out unscathed, Sergeant Makoto Narumi says "Team Leader" Sergeant Shinoa Hīragi led them well, and Shinoa panics briefly. Special Private Yūichirō Hyakuya offers to let her team rest while they keep watching. She takes him up on it.
Guren Squad arrives next. She reports to him and ends up crying when she mentions eight deaths. Lieutenant Colonel Guren Ichinose says its that type of mission and congratulates her on bringing seven of them back alive. Guren states this makes three nobles confirmed dead with five of their original targets left. He takes Shinoa Squad and Narumi Squad into his team to attack Thirteenth Progenitor Crowley Eusford, Seventeenth Progenitor Chess Belle, and Seventeenth Progenitor Horn Skuld and rescue hostages at Nagoya City Hall. When Aiko asks to join him, he teases her, saying that anyone who cries on the battlefield is not allowed. He orders her to wait half an hour for late squads and then proceed to Nagoya Airport.
After half an hour, five survivors from another team limp their way to her. She notices vampire helicopters arriving and orders them to flee to Nagoya Airport. She manifests Sankoujitsu, her archery weapon and shoots through the first copter.
Lacus Welt, René Simm, and Mikaela Hyakuya jump down from the second. Mika pins her down and tells her he has questions for her. As the vampires attack and capture her weakened team members, she orders them to "do it" before they are forced to talk. They obediently chomp into poison pills and die. She attempts to as well, but Mika sticks his fingers into her mouth and removes it before she can. She says he can torture her all he wants, but she will tell him nothing. Mika tells her to shut up before the other vampires realize she is not dead.
Perplexed, she speaks with Mika briefly. He asks her about Yūichirō. She hesitates before denying that she knows anything. He covers her mouth to prevent Lacus and René from hearing her and demands she tell him everything now. She insists she will not sell out her friends.
When Lacus and René talk to Mika, Mika reports that Aiko killed herself along with the other humans, surprising Aiko. Another vampire reports that all the vampires stationed underground were killed and claim that Nineteenth Progenitor Mel Stefano was murdered. René suggests they head to Nagoya City Hall.
Alarmed, she jumps to her feet and puts a knife to Mika's neck in an attempt to use him as a hostage. Lacus says that neither he nor René care if Mika dies.
Aiko whispers that Yūichirō is headed to Nagoya City Hall and says that Mika needs to stop the other vampires from heading over there. Mika grabs her wrist and crushes it, making her scream in pain, amusing Lacus. Mika monologues at her about her being a filthy, shameless human who betrayed her own comrades to save her own life. Catching onto his plan, she begs for her life, and he kicks her several yards. She promises to talk and says that the JIDA sent a platoon of fifty to attack the Automobile Museum and assassinate Seventeenth Progenitor Zane Lindau.
The vampires decide to act on the information out of fear for repercussions if they do not. Aiko asks Mika to kill her before they torture her for more information. Mika tells her to do it herself. She claims that would cast everything in doubt. As Mika leaves her behind, she jumps to her feet, manifesting her bow. She screams that the vampires will kill her anyway, so she will take at least one of them with her.
Mika calls her a fool before slicing through her chest and ending her life. With her last breath, she smiles and thanks him.
Powers and Abilities
Aiko possessed leadership skills. She was also attentive to her surroundings and was quick to act on her feet.
- Sankoujitsu (三光日 Sankoujitsu?, lit. "Three Light Days"): A manifestation-type demon weapon that takes the form of a bow and arrow.
- "STAY BACK!! The lieutenant colonel is at Nagoya Airport! We'll act as decoys and hold them off! You run and hide! Hurry!"
- —Aiko to a surviving squad when vampires arrive. ("Who's Pulling the Strings?")
- "Right now, Private Yūichirō Hyakuya... is headed for Nagoya City Hall. If you vampires head over there, all of the humans there, including Yūichirō Hyakuya, will be killed. Don't go. Please."
- —Aiko to Mikaela Hyakuya. ("Sword of Justice")
- "Because of what you said. You called the rookie 'Yu.' That's a nickname. I chose to bet on the hope that means you're close. Protect him, Vampire. Don't let the other bloodsuckers go to the city hall. And before you--"
- —Aiko to Mikaela on why she trusts him. ("Sword of Justice")
- "TH-THE JAPANESE IMPERIAL DEMON ARMY SENT A PLATOON OF FIFTY! ALL FIFTY ARE GOING TO ATTACK THE AUTOMOBILE MUSEUM! OUR ORDERS ARE TO ASSASSINATE THE NOBLE NAMED ZANE LINDAU!"
- —Aiko lying to the vampires after pretending to surrender. ("Sword of Justice")
- "...It worked. But do me one last favor, vampire... Kill me. Before they capture me and torture me for more information."
- —Aiko to Mikaela. ("Sword of Justice")
- "Good. Thank you."
- —Aiko to Mikaela when he kills her. ("Sword of Justice")
- Aiko's surname Aihara means "phase" (相) (ai) and "field, plain" (原) (hara).
- Aiko's first name means "draw, tie" or "patronage, favour" in Japanese.