Happiness 3 by Shuzo Oshimi

After succumbing to the urge to drink Yuuki’s blood, Makoto and Yuuki escape from the dangerous Saku with their lives…or at least, with what’s left of them. As Makoto, and now Yuuki, deal with their growing thirst for blood, the two struggle to hold onto what’s left of their humanity – and resist the urge to hurt the ones they love. But when Nora offers Makoto a form of salvation, will he accept, turning his back on his family and friends, or can he find a way to continue living in the only world he’s ever known?