The main heroine of “Tsukihime”, she is a blood-sucking vampire known to some as the “White Princess of the True Ancestors."

She came to the town of Misaki in pursuit of her nemesis, Roa (SHIKI), the serpent of Akasha, but in the process she had found herself “dismantled” into 17 pieces by Shiki Tohno.

With Tohno's help, she managed to destroy Roa and settled in the town.

Her fighting power is unparalleled, and it is no exaggeration to say that she is the strongest character that has ever appeared in the world of Tsukihime.
She's a very whimsical, cheerful figure in Tsukihime. Despite knowing the basics of the modern era, she is still unfamiliar with the social norms. She's the kind to get excited over trying a burger for the first time.

She also has an hypothetical evil version that had been manifested by the Night of Wallachia, but we can mostly ignore that. (Oh, and please check Neco-Arc's page since she's just a tiny goofier version of Arcueid!)