She is a member of New Light and was introduced in Volume 17.
Lessar is a member of New Light with black hair and a dragon-like tail accessory which allows her to keep her balance when jumping because she can jump very high, but is also afraid of heights, as shown when she had no problems jumping to the top of a building but then hesitated to jump back down.
She is the kind of girl who doesn't know how to keep a low profile. Lessar has so far made the most aggressive attempts at seducing Touma out of all the girls interested in him, and doesn't try to hide it. She once made a move on Touma while in a enclosed space in Russia but it is not shown what happened. After her clothes got wet from the snow and her bra could be seen through her top, instead of being embarrassed, Lessar is more annoyed that her 'secret weapon' to seduce Touma has been wasted after all of her preparation.