Komoe Tsukuyomi

Despite her childish and very short (135 cm) appearance, she is actually an adult and one of Tōma's teachers. This is proven by her apartment being littered with beer cans and cigarettes. She also contradicts her age by acting childish to her students, having a child-like crush on Tōma, and ending her sentences with desu, something a child usually does. This irony means that she is often regarded as one of the seven great mysteries of Academy City. She has major interest in studying pyrokinesis and performs magic once, when Index requires her to participate in a magical ritual to heal her wounds. The fact that she is able to do so indicates she has no esper abilities of her own.

(Source: Wikipedia)