Ai Death Gun

Sajimiya Reiji and Mijou Yashiki are partners who use their Death Guns to hunt a group of vampire-like beings known as Artemis, created due to a natural disaster that occurred a century prior to the events of the story.

When a group of Artemis that calls itself Pleiades begins to attack random humans and convert them, naive newcomer Takao Iota teams up with his two more experienced co-workers to try and hunt down the ones responsible.

(Source: MU)