Seraph of the End, Vol. 1

Yuichiro's dream is near-impossible, given that vampires are seven times stronger than humans, and the only way to kill them is by mastering Cursed Gear, advanced demon-possessed weaponry. Not to mention that humanity's most elite Vampire Extermination Unit, the Moon Demon Company, wants nothing to do with Yuichiro unless he can prove he's willing to work in a team—which is the last thing he wants!

Volume 1 of the Seraph of the End manga series by Takaya Kagami.