Sana is the daughter of the high priest who oversees the school responsible for training Mao, Hyakka, Kumon and Shiranui among other powerful onmyodo practitioners. Seemingly the sole female in a temple filled with men, she is an object of quiet desire for many of the pupils though only a few have been able to gain her attention. Mao pined for Sana silently and seemed to win her attention when her pet cat, Haimaru, allowed Mao to pet him, something only Sana had ever been allowed to do.
While Sana seems aloof from the daily work of the temple, in fact she is used by her father to enact powerful curses. At night while she sleeps her father is able to draw powerful curses from her mouth which he casts into spells and sends off through his underlings to craft deadly sutras. Sana seems unaware of this, though she too has her secrets from others. She has an infatuation with the earth-wielder Daigo who she would meet in private corners away from prying eyes.
Eventually her cat, Haimaru, was stolen from her and crafted into the powerful demon Byoki. When Byoki broke free he massacred everyone and in his battle with Mao Sana was killed. Mao was blamed for her death and has been hunted for centuries by the immortal survivors of the slaughter. With master and heir dead the once great temple was utterly destroyed leaving its esoteric teachings to become the stuff of legends.
However Sana's story does not end here. In 1923 in the wake of the Great Kanto Earthquake a veiled woman appeared with Hakubi. Calling herself Yurako the woman seems to have the face of Sana and her ability to speak powerful curses. Mao is stunned to learn that his first love may still be alive after so many centuries and even Byoki has stated he cannot believe the woman could truly be Sana. Ultimately it is revealed that this is a ruse, and Sana seemingly did truly die during the Heian era centuries earlier.
The Meaning Behind the Name - 紗那
Sana (紗那) is written with the characters for "gossamer". The kanji have little to reveal about Sana's personality. The woman who claims to be Sana in the 1920s goes by the name Yurako (幽羅子). The kanji here are interesting in their meaning- "hidden", "thin silk" and "child" which is a common female name ending.