Seraph of the End, Vol. 6 by Takaya Kagami

[Viz] In a post-apocalyptic world of vampires vs. humans, Yuichiro brings vengeance upon his vampire overlords! After trumpets of the apocalypse proclaim the fall of humanity, vampires arise from the shadows to rule the earth. Yuichiro wants just one thing—to get revenge by killing each and every vampire. The only thing standing between humans and complete slavery to vampires is their tenacity and Cursed Gear. Yuichiro has the first in droves, but to increase the amount of power he can draw from the demon inside his cursed sword, he enters a coma-like state to thin the barrier between human and demon. His power boost can come none too soon as the vampire queen reveals her plans to annihilate the human resistance.