Imadoki no Vampire: Bloody Bride

You play as a young vampire who has reached (vampire) adulthood. He is sent to earth to suck the blood of a girl with a 'platinum aura'. However the girl has to willingly allow him to suck her blood. The character is given three years to complete his mission.

The young vampire is sent to the human world in order to find a girl with that aura, having 3 years to complete that task. As a vampire, the boy must wander at night in order to find common girl and suck their blood, although he will usually find monsters with whom he'll fight in order to help him reach his adulthood.