Zero In

In the year 20XX, violent crimes with heavy weapons have been rising at incredible rates. The Japanese police, unable to combat it all, has authorized a private police force known as...Private Police (Minkei in the original Japanese) to assist with certain difficult situations. One of these Private Police officers is Mikuru Nazume, a high-school girl/gunslinger who uses a special technique known as "Command Zero", or "Zero In" to achieve great success in the field, earning her the nickname "No-Murder Mikuru". While on a mission, she saves Kou Shiraishi, a classmate of hers and son of a well known detective, and helps him resolve to join the Private Police. Soon enough, he is assigned to Mikuru's squad and assists her in the field.

Started in 2004, Zero In is an ongoing manga by Sora Inoue (formerly the illustrator of Real Bout High School) about Mikuru and Kou's work in the Private Police. Keep in mind, though, that crime-fighting isn't their whole lives - both Mikuru and Kou are still very much regular students, just ones who work part-time as Rent-A-Cops. Really, really badass Rent-A-Cops.

This Manga contains examples of:

 * Badass in a Nice Suit: Misono dresses exclusively in suits; she is also the most ruthless member of the team. Put it this way: she agreed to stop killing people about 10 chapters after her introduction...and she still has one of, if not the, highest body count in the series.
 * Breather Episode: Chapters focused on Mikuru and Kou's school life are usually much lighter and more comedic than the main bulk of the story, and tend to take place between more action-oriented arcs.
 * Also, Chapter 30, a.k.a. the Ping-Pong chapter. Nothing more needs to be said.
 * Captain Ersatz: Mikuru's mom is basically Rally Vincent.
 * Dark and Troubled Past: Mikuru, Kina, Misono...y'know, it might be shorter to list characters without one...
 * Diabolus Ex Machina:
 * Exty Years From Now/Twenty Minutes Into the Future: 20XX, which doesn't seem too different from now, aside from the whole "exploding violent crime-rate" thing.
 * Well, and that private gun ownership is apparently legal in Japan. And extremely advanced bulletproof armor that wears like leather.
 * Five-Man Band
 * The Hero: Mikuru
 * The Lancer: Misono
 * The Big Guy: Ross Tomozou
 * The Smart Guy: Kou
 * Da Chief: Nanami
 * Gun Fu: Mikuru's "Command Zero" and "Zero In" in general, which was developed by her Grandfather and mastered by her Father.
 * Happily Married: Nanami and her husband, as shown by an omake chapter. They have a 10-year old child.
 * Insistent Terminology: Tomozou always calls himself "Ross", part his "Gun from LA" persona. No one else goes with it.
 * The Nicknamer: Ross Hana Tomozou, who comes up with very odd nicknames for most people he meets. The most common one he uses is "Russian', for Misono, as she reminds him of a Russian Blue cat that his sister owns.
 * Non-Action Guy: Kou is classified as a "Keeper", which basically means he provides a support role. Extremely justified considering the number of actual fighters he works with, so he never has to be anything more than that.
 * Oblivious to Love: Mikuru has no clue that Kou is in love with her. Kou in turn, is unaware of Noriko's feelings.
 * Mikuru and Kou do realize their feelings in Volume 8 and 9
 * Ordinary High School Student: Mikuru and Kou may be awesome Private Police officers, but they're still mainly students.
 * Stalker with a Crush: Played Horrifically.
 * Team Mom: Nanami, appropriately called "Leader". It helps that she's actually a mother outside her job.
 * Thou Shalt Not Kill: A very big theme in the series. Mikuru believes this, and is able to enforce is with her skill, earning her the "No-Murder" nickname. Misono, on the other hand, does not, which is the source of a lot of the feuding between the two.
 * Too Cool to Live:
 * Training From Hell: The Minkei training.
 * Wham! Episode: