Cis

Cis (シス) was an android created by Rotwang whose system had information on all currently active heroes.

Story
While in transport, the vehicle carrying her was struck by lightning and she escaped. Keith met her in a park and, though she seemed only able to say a set number of phrases ("I don't know", "Yes", "No", "I'm sorry", and "Why"), his conversations with her have boosted his confidence after having lost his title as King of Heroes, eventually leading him to fall in love with her.

The lightning strike apparently also affected Cis' system, causing her to go into attack mode whenever "Heroes" are mentioned.

As a result, she fought with Kotetsu and Barnaby and was easily able to overpower them due to her superhuman strength and lack of any concern for her body's well-being.

She was ultimately destroyed by Sky High, who was unaware that the girl he met in the park and the android causing havoc were one and the same.

Trivia

 * Cis has a similar appearance to and the same seiyu as Dorothy from The Big O. Subsequently, the creator of The Big O is also the director of Tiger & Bunny.
 * Official materials have listed her name as "Cis", "Sis", and "Six", so there appears to be no definitive romanization. The fanbase favors "Cis",