A character of Shakugan no Shana. Shana takes over Yukari's identity using the remains of her "Power of Existence" (life force) after she became a Torch (an entity replacement for a human whose Power of Existence has been significantly depleted) and eventually disappeared.
To distinguish Yukari from Shana, one must consider the following:
Yukari's eyes were purple; Shana in neutral form has brown eyes.
Yukari had small twintails. Shana rarely wears them, but when she does, they are in huge tresses.