Takitsubo Rikou

Takitsubo Rikou (滝壺 理后) is a member of ITEM. She later leaves the group along with Hamazura Shiage, after she becomes extremely weak due to abusing an ability-enhancing drug.

Appearance
Rikou is usually seen wearing her pink sports outfit, so much so that Hamazura Shiage stated that she would probably wear it to a wedding or funeral. She also has deceptively large breasts underneath her sports shirt. Rikou has been described as someone who chooses clothes based on functionality and not on appearance, similar to Yomikawa Aiho

Personality
Rikou's personality resembles that of Aisa, in that she is rather blunt and rarely expresses her inner-thoughts. Despite the fact that she shows little emotion, she does care about her fellow 'ITEM' members and in particular, Shiage, whom she is in love with. Even with her friends she would normally behave quite cold and detached but not in a bad way, she has been described as "lethargic" instead of stern or aloof.

Whenever a character has been put in a ridiculous position she usually address him / her with encouraging lines such as "Don't worry. It's ok, I'll support you", though her courtesy and condescending behavior will probably have the opposite effect and would bring a heavy blow to whoever she was trying to cheer up.

It should be noted that Rikou as shown a selfless side of herself several times, in many opportunities she offers herself as a bait to lure out enemy while her friends escape regardless of her own physical state; in other times she refutes the possibility of being rescued from danger as the risk is too high, it is also partly because of that selflessness that Hamazura Shiage wants to "bring happiness" to Rikou if possible.

As of New Testament, Rikou has developed a very possessive personality towards Hamazura and reacts strongly towards any sign of unfaithful behavior, to the point where Hamazura described that attitude as "a dangerous light in her eyes". It should be noted that Rikou has shown jealousy even in situations where Hamazura himself refutes that nothing can possibly be happening (for example, when Fremea was innocently sleeping on Hamazura's lap ).

Sister's Arc
Chronologically, she first appears in Toaru Kagaku no Railgun with the rest of ITEM in order to stop Mikoto from destroying a research facility. She helps Mugino hunt down their target only to become weakened due to the use of the drug, Body Crystal.

Battle Royale Arc
Out of all of the ITEM members she is the only one to treat Shiage with kindness, which ultimately leads to their relationship. At one point, she meets with Hamazura while he is disposing of a corpse in a furnace, and she asks what is wrong. However, he ignores her and says outloud about what a person's life is and when did Level 0's lives become a cheap thing. When SCHOOL finds one of ITEM's hideouts, Rikou knows the SCHOOL is likely after her due to her ability. Hamazura initially tries to get her into an elevator while he distracts Kakine, but she manages to push Hamazura into the elevator instead because she did not want him to die. She tells Hamazura that she does not want him to become ash which has a great affect on him.

In her fight against Kakine Teitoku in vol.15, she tries to manipulate his AIM field and use it in the form of an attack against him, forcibly attempting to make him lose control of his power and go berserk. This fails however, and due to her condition and the difference in their power, she still loses. However, when Hamazura returns, Kakine chooses to simply spare her life since if she forces herself to use her powers too many more times she will die, but she might be okay if she does not use her power anymore.

Mugino initially plans to force her to use Body Crystal again to find the members of SCHOOL, but Hamazura defies her and runs away with Rikou. Along the way, they run into Aiho Yomikawa and Hamazura begs her to take them somewhere safe. Before they could leave, they see Mugino with half of Frenda's body. Hamazura manages to convince Yomikawa to take Rukou away from the area while he kept Mugino busy.

Dragon(=/ Angel) Arc
After leaving ITEM, she is admitted into a hospital for treatment. However, even after being discharged, she is too weak for things beyond ordinary life. Even in that weakened state Rikou sees herself involved in a terrorist hostage situation and in terrorist attacks, and later is faced against Mugino Shizuri.

Fiamma of the Right and World War III Arc
After she and Hamazura Shiage after they hijack a jet from Academy City in District 23 they arrive in Russia. Later, her condition becomes worse and she is handed over to a doctor only to find out that she can't be healed with the current technology in Russia. Shiage then tries to hide her whilst fighting against pirates alongside a villager and a soldier.

In the epilogue of volume 22 it was revealed to Shiage, Rikou and Mugino that Rikou is a very valuable test subject who has the potential to be the 8th person to reach level 5. Even more important is that since her power affects ‘Personal Reality’, it is theorized that Rikou's ability has an incredible potential; such as changing a person’s level or giving a person multiple skills. To put it simply, it would be possible to give Hamazura Shiage the Railgun’s power, or Mugino Shizuri can be demoted down to a Level 0. For this reason Rikou was to be retrieved alive while Shiage was not.

Freshmen's Attack
After volume 22 she becomes part of the new team "ITEM", which is composed of Shiage, Mugino, Saiai and herself, she has recovered to the point where her health is outside danger as long as she doesn't use Body Crystal, thus she is unable of using her ability. She claims that she still gets "feelings" from her ability from time to time, and decides to follow those "signals" while ITEM decided to play hide and seek with Shiage; this is played comically, though, while her instinct couldn't lead her to Hamazura, she could perfectly and accurately notice when Hamazura was "flirting with another girl", regardless on how far they were apart.

Abilities
Rikou's ability is AIM Stalker (能力追跡), which she uses to track down other espers. To use this power she needs to consume what is known as Body Crystal, and in recent chapters, continued use of the drug has worn her body down to the point where she will collapse and become seriously ill if she uses it again. Rikou developed in such a way that she can only use her ability by consuming this drug, as part of an earlier project to create a Level 6 before the 'Experiment' involving Accelerator, and thus she can no longer develop through the normal methods other espers go through.

She states that her ability allows her to steal other espers' abilities by memorizing their AIM field, potentially allowing her to become the eighth Level 5 esper in Academy City. This fact is also mockingly mentioned by Kakine Teitoku after their fight, who states what a shame it is that she has to rely on a drug to use her powers.

Due to over-use of Body Crystal, the poison in her body makes it she will self-destruct if she uses her ability any more. This problem was eventually healed by Elizarina when she and Shiage managed to escape from Academy City.

In the epilogue of volume 22 she manages to use her ability to help Mugino's aim with Meltdowner and in turn that move was used to save Shiage's life. This reinforces Academy City's view that Rikou can affect other espers' Personal Reality, according to ITEM's backer on the Board of Directors.

Quote

 * (To Frenda in the Railgun manga, talking about ITEM) : "I'm fine... This is the only place where I belong, after all..."
 * (To Hamazura, Vol 15) : “I told everyone about what you said by the furnace. I don’t want you to become ash like that. Don’t worry. I’m a Level 4 and you’re a Level 0. So I’ll protect you, Hamazura.”
 * (To Hamazura, Vol 21) : “It’s okay, Hamazura,” -- “Even now, you’re fighting to protect me. So you aren’t pathetic.”
 * (To Hamazura, NT1) : "…Don’t NTR anyhow, Hamazura, you’re mine" (NTR is a "genre" within the visual novel world were a lover is stolen away by another person).
 * (To Hamazura, NT2) : “…Kinuhata always says you’re super Hamazura-y, but I’m a little disappointed that it’s at the level of a wild beast…” -- When Rikou found Fremea and Hamazura on what she perceived as a unsightly position.

Trivia

 * It is uncertain if Body Crystal - the drug she uses to power her abilities - is a by-product of Therestina Kihara Lifeline's research. However, both Body Crystal and Crystallized Esper Essence seem to have the same effect on the user.
 * Rikou can fall asleep with her eyes open.
 * It is discreetly implied that Rikou might be a Child Error.