Takashima is first introduced after Tamaki collapses a tower on Ganta. Ganta goes to her office, where she fixes him up and tells him about the candy. She appears a second time when she analyzes Senji's X-rays.
However, when Senji loses his battle against Ganta Igarashi, she more than happily removes his right eye and gains pleasure doing so, therefore exposing her sadistic side.
Later on, when Minatsuki faced her penalty of losing an organ at random, she only had to lose some of her hair as it had been rigged by the members of Scar Chain; this caused Takashima to become furious.
She has been seen helping Tamaki with his plans on the Forgeries experiments on random Deadmen. She has also given Azami Midō her Snake Branch of Sin, making her a Forgery.
After the Deadmen defeated the Forgeries, she broke down crying and doubts that they could defeat Wretched Egg. However, Tamaki strangles her for doubting his goal to defeat Wretched Egg.
Near the end of the DW revolt arc, she is seen busy in her laboratorium and eventually killed by an unknown being (most likely the Wretched Egg).
- In an extra short-story in Chapter 12, incidentally tilted 'Perfect Man', Rei is shown treating an anatomical mannequin named "Tsutomu" as a lover with actions such as complaining to him about not being able to remove an organ or two from Minatsuki and that there's nothing wrong with her wanting to do so. She also accuses the mannequin of being a flirt because she can see right through him.
- In the anime's ending sequence she is implied to having worked in the same hospital as Karako once did.