Takitsubo Rikou

Takitsubo Rikou is a member of ITEM. She suffers from brain damage after fighting and being defeated by Teitoku Kakine in vol.15; as a result, she can no longer use her esper abilities. Her ability was the AIM Stalker which she uses to track down the esper, she needs to consume what's called 'crystallized esper essence' (see Railgun Anime episode 22 for more details on the essence) in order to use her power, however continued use of the drug has worn her body down to the point she would break down if she uses it again once or twice. She was developed through such a way she can only use her ability by consuming the essence, as part of a earlier project to create a Level 6 before the 'Experiment' involving Accelerator, and thus she can no longer be developed through 'normal' methods other espers go through.

She also states that her ability allowed her to steal other espers' abilities by memorizing their AIM, potentially allowing her to become the eighth Level 5 esper in Academy City. This fact was also mentioned by Kakine after their fight, saying it's such a shame she had to rely on the essence to use her powers.

In her fight against Kakine in vol.15, she supposedly tried to manipulate his AIM field as a attack against him, forcibly attempting him to lose control of his power and berserk, and also attempting to use his own ability against him. Though due to her condition and the difference in their power she still lost.

She is currently escaping from Academy City' forces in Russia with Hamazura Shiage and the help of Acqua of the Back.