Saya Terumi

Saya Terumi is a mysterious girl that is the younger sister of Naoto Kurogane and the cousin of Haruka Hayami. Her Drive is Soul Eater. Due to her frail body and Drive, her life-force value changes constantly, with the only shown value being 7946.

History
Descended from the Amanohokosaka Clan. When she was 8 years old, Saya gained the Soul Eater Drive, and was imprisoned by her clan for slaying the entirety of the Terumi Clan, save for her mother and brother; but her power proved too great for them as they were unable to bind her for long. Saya seeks the revival of the Terumi Clan and requires the eye of her brother, Naoto Kurogane, in order to do so.

Bloodedge Experience — Part 1
Saya is first seen in Chapter 6: Interlude when she rings the door clock on Naoto's apartment. When Haruka opened the door and saw her, she immediately ran to Naoto and dragged him to the entrance. When Naoto saw Saya he was completely lost for words and could not believe it was her, but she made it sure that she was who she was and called Naoto big brother.

Bloodedge Experience — Part 2
Following her entrance into the Hayami household, Naoto asked Saya why she was in there, being handed a letter from Mei Amanohokosaka, the current head of the Amanohokosaka Clan, to explain the situation. Saya then asked Haruka for some alone time with her brother, which the left two alone as both Haruka and Raquel Alucard began to leave the room. After being told to leave from her older brother, Saya revealed her motives for arriving and grabs his throat, pushing him to the nearby wall, and uses Soul Eater to drain his life. She taunted him, saying that she will take his two eyes and murder him; however, she was interrupted as Raquel dashed through the room and the two began to briefly fight until the young girl fled, having the last word as she announced that this encounter was only a greeting. She later fought, and killed, one of the Apostles with her Drive.

When Saya found Valkenhayn R. Hellsing and Relius Clover, she viciously attacked the former for having killed Naoto twice. After a small amount of fighting, Saya began to use her Drive when she got a grip on Valkenhayn, intriguing Relius; she taunted the puppeteer, asking him if he was going to save Valkenhayn, but she collapsed as she had exceeded her time limit. Thankfully for her, Naoto came to her rescue, preventing her from being killed, but this was not enough as Spinner Superior's darkness kidnapped her while she was still recovering.

Spinner had one of his most powerful bugs hold Saya and force her to drain the life of everyone in Shin Kawahama City. As Naoto and Raquel fought to get closer to the bug, Naoto found himself in a good position to kill his little sister, but he refused, instead ripping the bugs legs that were holding the young girl, and then going on to kill the bug himself. When the fight between Naoto and Spinner occurred, Valkenhayn and Relius stole the unconscious Saya while everyone was distracted; she was presumed missing by Naoto and Raquel sometime later.

Personality
At first glance Saya seems like a normal girl with good manners and polite speech, but beneath that appearance she is someone that will use deadly force with no hesitation in order to get rid of obstacles. She is proud of being part of the Terumi Clan, and is even obsessed with it to the point she will kill her brother to revive it, even though she shows anger of hearing Naoto being killed by Spinner's bugs and Valkenhayn Hellsing.

Appearance
She has red eyes and long purple hair. She wears a kimono and carries a bag which holds a katana inside.

Powers and abilities
Contrary to her frail appearance and young age, Saya is tremendously powerful. Her Drive, Soul Eater (ソウルイーター), drains the life force of anyone she touches; should she kiss them, the effect is much more powerful. Unfortunately for her, Saya is still remarkably frail, with her Drive being the only viable way for her to make herself effectively stronger.

Saya can only fight for around three full minutes before collapsing. In order to save herself from any danger while in this state, she can use magic in order to lend her some temporary strength.

Trivia

 * Saya has a striking resemblance to Hades Izanami not only in appearance, but personality. However it was confirmed by Naoto that they are not the same person.