Maria Totsuka

A teenage human girl who initially encounters Lucifer during a brief stopover in the middle of her descent to Hell. Possesses an unusual gift of sight, which enable her to see celestial and demonic beings. Maria becomes Lucifer's unwilling servant when Lucifer rips out her heart, granting her immortality and eternal youth. At their first encounter, Lucifer also infused Maria with a part of her angel's blood, enabling her to find her offenders in order to exact revenge on them.

(Source: Wikipedia)