Deathless

Mizuki is a bespectacled university student who lives with her grandparents. One day, there's a little trouble with thugs, and two strange women, Suzaku and Kamado, step in. That night, a yakuza underling comes and murders Mizuki. Luckily, Suzaku comes along and (kind of) resurrects her! It turns out that Suzaku and Kamado are deathless beings who consume time from the people around them. Now Suzaku and Mizuki appear to be sharing the same body.

(Source: MangaHelpers)