Happiness (ハピネス, Hapinesu) is a Japanese supernatural manga series written and illustrated by Shuzo Oshimi. It began its serialization in the Bessatsu Shounen Magazine in 2015. The series is published by Kodansha in Japan and by Kodansha Comics USA in the United States.
Makoto Okazaki is your run of the mill high-schooler, a perfect bullying target and a closet pervert. One Night he decides to return a DVD to a friend of his and ventures out into the night. He notices a person on a nearby rooftop. The person lunges at him before he is able to make sense of this, and bites into his neck, drinking blood. Then, they stop. At this point, Makoto notices that the attacker is a beautiful girl who asks him: "Do you want to die or become like me?" He decides to live...
Official English manga site