In Reiko's first appearance, she had shoulder length light purple hair and sharp brown eyes. She had an average height and a slim build. With her second appearance, her body type remained the same, but her skin became more fair. She now had long black hair and a more pointed face. She was often seen wearing formal attire and lip stick.
Reiko was a highly intelligent parasite, as she often studied the human psyche in hopes of understanding their species better. She was initially just as cruel as her fellow parasites, though she did show restraint about killing humans unlike A.
Reiko was also highly philosophical and inquisitive; she had sex with another Parasite-infected human to see what would happen if she got pregnant and was intrigued when she learned the resulting child was fully human. She also didn't kill Shinichi, despite him knowing too much, because of his unusual symbiotic relationship with Migi and especially when she sensed that he himself is no longer completely human.
After giving birth and raising her child, she began developing and showing human emotions, such as laughter and love towards her son. She sacrificed her own body to keep her son safe, as the police shot a barrage of bullets at her. Before succumbing from her wounds, she revealed that she truly believed humans and parasites to be the same.
After the Parasite took over Ryōko Tamiya's body, the Parasite took the name "Reiko Tamura". Reiko has scientific inclinations, and is driven to discover the biology, origin, and purpose of Parasites. Reiko discovers—by becoming impregnated by another Parasite named Mr. A—that a pregnant Parasite will bear a normal, human child, and that Parasites have no apparent means of reproduction.
Reiko kills Ryoko's mother who learns that daughter quit her job but she discovered she is not Ryoko used be
Reiko is more logical and reasonable than many other Parasites, and allows Shinichi to live unmolested largely because she finds him an interesting anomaly worthy of study.
She eventually gives birth to Mr. A's baby; after betraying her fellow Parasites and killing quite a few of them, the police brutally kill her. The baby survives because of her decision not to fight back against the police. Her own sacrifice restores Shinichi's humanity, making him shed tears.
Powers & Abilities
As a parasite, Reiko has the basic abilities to shapeshift her head, and maximize the physical potential of the body she's controlling. She can harden her cells for offensive and defensive purposes.
Her high intelligence allowed her to make use of unorthodox tactics when engaging enemies. When targeted by three of her own kind, she tricked them into believing she had gone insane when she split her parasite in half. Believing her to be suicidal, she was able to lure away Kusano, kill Maesawa by allowing the parasite to burrow and destroy him from within and then trick Kusano into killing Hikawa by burrowing into her and forcing her to attempt to kill Kusano. He kills her, allowing Reiko to sneak up on him and kill him when he unintentionally jams his ability to sense other parasites when he hacks Hikawa up.
While in the Live Action film, she can able to split her parasite in three, using them to pierce the heart of three of her own kind from behind, killing them without letting them notice. She can also extend her hair and wrap them on her child to protect him from the police's gun shots.
In addition, her intelligence and interest in the human mind allowed her to more effectively blend into society.