Sister Red

From the DrMaster manga outlet site:

This is the story of Mahito, Alice and the "The True One"

All sorts of odd things begin to happen when Mahito survives being rundown by a car traveling at high-speed. What lurks behind the world of the living? What is it that hides just out of sight of human perception? There is more to our world than our eyes reveal, as Mahito, a young High School girl, is about to find out. Questions mount as one thing becomes painfully clear; Mahito did not survive her accident at all.

Modern-day vampires, the occult and hunters of the undead? 'nuff said!

When walking home, Mahito suddenly gets killed by a hit-and-run by some drunkards. When she thought she had already died she was revived, in her house without a scratch. Thinking it was merely a dream she thought nothing of it until Alice appeared. Alice was a median that was already dead but was alive due to Scarlett's heart, Alice had one half of Scarlett's heart while Mahito had the other half. That meant that the only thing keeping mahito alive was Scarlett's heart and that wasn't even hers! But many people sought the heart because it brings immortality. But Mahito is still clinging to life because of her half-sister Erika and uses the Scarlett power with Alice to defeat the true enemy that poses a threat, Yuri, who is Alice's brother who is to be destroyed.