Tate Karito is a freelance bodyguard and former operative of the National Police Agency's Special Assault Team, who's a bit of a SecretKeeper, and has a high-tech artificial metal arm that serves as his weapon of choice. With a shady past and a penchant for protecting anyone, so long as they solve his bosses' riddles and can pay his fee, Tate follows whatever path is laid before him.

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!!This series provides examples of:
* ArtificialLimbs
* AsTheGoodBookSays: Zero does not quote directly from the bible, but his monologues have biblical motifs.
-->'''Zero''': God created Adam from a lump of earth; Eve was created from Adam's rib. Death is nothing but returning to the start of life. Therefore, I mutter prayers... "Ashes to Ashes, Dust to Dust".
* BadAss: Tate, obviously. Zero can qualify, even if he IS a bad guy.
** In later chapters, many, ''many'' characters qualified. Even [[TokenMiniMoe Anna]] has her moment, too.
* BadassGrandpa: Sakakai Souhei, the old sniper who [[spoiler:managed to ScopeSnipe while dying]], and with a comparatively outdated rifle to boot
* BadassLongcoat: sported by Tate, Zero, [[spoiler: and Jesus]].
* BarehandedBladeBlock: Tate does this with ''bullets'', thanks to his ArtificialLimbs.
* BladeBelowTheShoulder: [[spoiler: Tate's got a blade hidden and ready to use if his robotic arm is out of use.]]
* BulletCatch: more like "deflecting", but close enough.
* ButNotTooForeign: Anna is half-Japanese, half-Sicilian
* ChainLetter: The concept of this was explained by a corrupt police superintendent on how "Angel" obtains its manpower.
* ChekhovsGunman: [[spoiler:Hitomi-chan. An actual gunman, no less.]]
* ChickMagnet: Tate.
* ComicBookFantasyCasting / {{Expy}}: Zero looks ''exactly'' like JeanReno/[[Film/TheProfessional Leon]] in Film/TheProfessional. Chihiro looks like [[Anime/NeonGenesisEvangelion Rei]] with black hair and GenkiGirl tendencies.
* {{Crossover}}: Some characters appear in UntilDeathDoUsPart.
* DirtyCop: [[spoiler: Some of the police officers Tate meet are corrupt, working in an organization called "Angel" as they sell evidence from the Tokyo Metropolitan Police's evidence vault to criminals. One of them tries to coerce a young detective to join them before he was killed. But not all of them are bad as a few of them are [[{{Blackmail}} forced]] to join "Angel"]].
* DudeWheresMyRespect: Averted. Tate is so respected in the [=SAT=] that he was allowed to be in one of their exercises as an Op-For. He's also a legendary bodyguard in the criminal underworld.
* ElitesAreMoreGlamorous: The National Police Agency's Special Assault Team. And yes, they're the elite civilian anti-terrorist/crime unit. Like most elite military/police units, their names are protected so no one knows who they are.
* EvenEvilHasStandards: Zero helping out an ex-hacker by killing the yakuza group after being kidnapped.
** Uno, an ex-JGSDF soldier who specializes in hunting humans in his officer days, puts down his K-9 dog after being wounded by Tate. He has less respect for humans, however.
* EvilCounterpart: Zero to Tate. He's not really evil though. [[spoiler: Jesus joins in later on, still not really evil. It's just a case of one side being the shield and the other side being the spear. Their philosophies also contrast each other in that one side vows to never kill while the other will kill whenever it's deemed necessary.]]
* FairCop: Youko, with a dash of CowboyCop.
* FeelsNoPain: Zero
** BlessedWithSuck: Zero actually tells Tate that he's jealous of him because he can still feel.
* GoMadFromTheRevelation: [[spoiler: Angel, a LivingLieDetector, has this effect on most people she met as she reveals their darkest desires and lies. She's also able to break their minds, apparently.]]
* HarmfulToMinors: [[spoiler: Zero's past. His family was killed in cold blood, and he became a hitman in order to exact revenge of the murderers.]]
* HeelFaceTurn: [[spoiler: Chihiro]]
* HeelFaceRevolvingDoor: [[spoiler:Zero, Jesus and Aki.]] Friends today, enemies tomorrow describes their relationship with Tate perfectly.
* LivingLieDetector: [[spoiler: Angel. No, not the group. Her.]]
* MillenniumBug: Koumoto Youji was originally hired to prevent damage from it.
* MyHeroZero
--> "They call him 'Zero'. Zero blood, zero body temperature, that kind of derivation."
* PunchClockVillain: Zero. He'll stop at nothing to kill his target, but he'll drop whatever it is he's doing if his employer cancels the contract or became unable to pay him.
* ScopeSnipe: How [[spoiler:Hitomi-chan]] is killed
* ShipTease: Tate and Youko, Tate and Anna (though he sees it more as a father-daughter relationship... probably), Tate and [[spoiler:''Angel'']].
* ShowSomeLeg
* SniperDuel: part of the aptly-named "Sniper's Requiem" arc.
* TheStoic: Tate
* ThouShaltNotKill: Tate's creed. [[spoiler:Until you push his BerserkButton.]]
--> '''Tate''': I will not kill, nor will I assist in anything leading to killing....
* {{Yakuza}}
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