From MangaHelpers:

In the near future, Japan has passed legislation making it legal for everyone over the age of 14 to carry guns for self-protection. Now, just about everyone carries a gun, including middle-school students! There are rumors of a mysterious legendary gunfighter, "Thousand-Killer Wendy," who fights against evil. Many criminals and others seek to draw her out, to make their names by killing the notorious Wendy. However, "Wendy" is actually three middle school girls.　Takatori Sally's low blood pressure and low blood sugar lead her to eat and sleep a lot, but she's still an awesome gunwoman. Shinonome Ma-chi, who specializes in sniping, has difficulty interacting with men, particularly handsome men. The third friend, Andou Misa, is the brains of the operation, and she deals with all the team's technology-related needs. Together, they'll do their best to handle whatever comes their way! [tethysdust]