The adventures of a group of people who hunt "witches", that is, people born with specific genetic superhuman abilities that many people associate with magic. It's implied in the opening credits' Fauxlosophic Narration that they aren't just a Witch Species but may have been a culture or civilization that ruled over man until deposed or self destructed. The protagonist of the series is Robin Sena, a witch herself with the ability to conjure and control fire.The main themes of the series involved the moral responsibility that these powers imply, and how many witches fall to With Great Power Comes Great Insanity. Other themes were isolation and persecution; witches have a hard time assimilating and living among humans while controlling their dark urges. In the second season it's revealed that even innocent witches all live in fear of being killed or disappeared by the likes of Robin's witch-hunting group if their powers are discovered. Robin herself battles with the fear she will one day become drunk on her power and be hunted by her friends as a witch.The show's format was notable, because for the first half of the series, the plot is entirely done in a Monster of the Week fashion, with the second half of the series abruptly starting an overall arc.
This show provides examples of:
All Your Base Are Belong to Us: SOLOMON does this to the STN-J mid-series. Made especially shocking by the fact that Robin was living there at the time, because they already did the same thing to her house!
Chief Inspector Shintarō Kosaka is the STNJ's boss and replaces Zaizen at the end. Though there's probably a Bigger Good in SOLOMON.
Another case could be made for Todo, depending on one's views on Robin's heritage.
Blunt Metaphors Trauma: Robin has a difficult time grasping the intricacies of the Japanese language, to say nothing of the customs. (Contrary to Robin's belief, the Japanese do not have a custom where they eat soba when saying goodbye.)
The Chick: Yuriko Doujima, whose the only girl of the group before Robin comes and is definitely the most girly with her fashion magazines and gossip. She comes into her own when it's revealed she's a double agent.
The City Narrows: The Walled City taking its name from the real world's Kowloon Walled City.
Cool Shades: Robin picks up a pair after leaving the STN-J and taking a job as a bike messenger.
Come with Me If You Want to Live: When the STN-J HQ is attacked and all but Robin are gunned down, Amon appears and grabs her arm and says "follow me". At this point neither she nor the audience are sure which side he's on. Technically not the beginning but rather the start of the story arc.
Conspicuous CG: There isn't any in the animation itself, but there are a lot of very conspicuously CG backgrounds.
Some witches use symbols that can be recognized by other unrelated witches, which implies that there is a a coherent system in use among them. One witch even contacted her sister's ghost for a revenge plot with a ritual that Robin recognized.
Just five years pre-series the STN used anti-witch bullets with carvings to ward off evil, and someone in the main narrative still does.
The Empath: Miho Karasuma, though she uses psychometry, is notable because her power is useful when used.
Equivalent Exchange: The power of a witch who can save one life by taking another. Notable for being the first witch that's A Lighter Shade of Grey and thus bringing a more complicated morality than what had existed earlier.
Faceless Goons: Employed exclusively by the Factory, from their hazmat-suited crime scene techs to their scary dark-grey soldiers.
The Glasses Come Off: Inverted. Robin's aim isn't that great at first. Then, she visits the optometrist and it turns that out her powers make her eyesight temporarily worse. Whenever you see her with glasses on, something's gonna burn.
God Is Good: While the head honcho himself doesn't make an appearance, Amon has this to say: "God doesn't forsake any of his children." The Big Bad is more of the opinion that Good Is Not Nice and that God struck down the witches long ago.
Good Shepherd: Father Juliano comes off more as this despite the generally dark religious tone. He genuinely thought witches were dangerous but despite that he couldn't kill Baby Robin, even though he know what she was. Instead he raised her as his own and admitted that his fear of witches (the emotion driving the Big Bad) is a weakness of his own heart, and no fault of the witches.
Freudian Excuse: Nagira asks Amon if he hates witches because his mom awakened as one and, in doing so, ruined their relationship. Amon says 'yes'.
Improbable Hairstyle: Subverted, Robin's hairstyle seems improbable at first glance, but it's shown to be held in place by a number of hairpins and hair ties. The rest of the cast generally has realistic normal hair.
Kansas City Shuffle: Amon does this by directing Robin to burn a hole in the STNJ's wall before sending her down a secret entrance in the floor, making their pursuers think she escaped through that hole and not follow her.
Karmic Death: While this would appear to be the case with Zaizen using the perfect Orbo he captured innocent witches to make, he doesn't die from its use... though he might have if Robin's flames hadn't reached him first.
Knight Templar: Zaizen is revealed to be this at the end. He commits atrocities without flinching, convinced of his own righteousness, refuses to listen to anyone or anything that contradicts his plan, and at the end even believes he has a Mission from God. Naturally, he's a villain.
Lady and Knight: Amon and Robin play with the trope. Robin looks like a victorian lady in her usual dress and is seen as the Dark Lady by many because of her heritage and some of her actions are brutal considering what the rest of the team does, but at heart she's a Bright Lady trying to do what's right. Amon ultimately betrays both Zaizen and SOLOMON to protect Robin from danger and is seen as a Dark Knight who's gone rogue, though he wavers back and forth. Robin herself calls him her "watch dog" because he will make sure she survives unless she loses herself to her power. At which point he will kill her himself.
Loners Are Freaks: Amon thinks so. "Witches are loners. It's part of their nature." But not really. One witch was an engaged businessman and even the witch that spent all her time alone in her apartment had living dolls to keep her company.
Lonely Doll Girl: There was a witch with multiple personalities manifesting through her dolls; personalities which considered any slight to her as "Unforgivable!"
Lovable Rogue: Nagira, the pachinko-playing lawyer layabout, is a great ally to Robin.
Only One Name: Amon. It might be his first name. It might be his last name. It might be an alias. It's all you're getting.
Personality Powers: Noteworthy in its aversion. Since powers are tied to genetics and spiritualism, the writers had every excuse. However, Robin is shy and demure, in contrast to the typical personality that one would expect from someone with her powers. Karasuma, by contrast, probably would've been an insightful person even without Psychic Powers.
Power Nullifier: Orbo, bane to witches everywhere. Their powers are limited or totally useless against people wearing it and bullets filled with it can negate their powers.
Power at a Price: The downside to Orbo is that it weakens the hunters using them as well. The original version causes a 30 percent decrease in efficiency and improved versions actually hurt them.
Romanticism Versus Enlightenment: The conflict between inherent witchcraft and manufactured Orbo, complete with a Byronic Hero love interest and neo-Victorian costumes, just in case anyone failed to notice the Victorian atmosphere.
Sinister Minister: Subverted and then defied. The Inquisitor is more of an official than a minister and less "sinister" than playing the "bad cop", and Father Juliano, Robin's guardian and grandfather tried to be this trope but raising Robin mellowed him out. Instead of condemning her, he blesses her.
The Stoic: Amon doesn't express emotion and goes about his business in a calm and efficient manner.
Team Mom: Harry for the STN-J. The members go to his cafe for emotional support and guidance. He makes special tea for them when they're sick. After the Wham Episode he hugs Robin and says "Welcome home."
Took a Level in Badass: Robin, after "Loaded Guns" gets an overall magic boost after she realizes she is the true Fragment of Wisdom.
Trademark Favorite Food: Michael loves food in crinkly aluminum bags. (The diet comes standard with the computer, apparently.) Robin's poor sleep habits are supplemented by large amounts of coffee.
Ultimate Job Security: Dojima comes in late, leaves early, takes extra-long breaks, and spends most of her time looking at fashion magazines, plus she was only hired because of who her father is. Subverted in that she's really there as a spy for the parent company, which is suspicious of the new procedures instituted by the Japan branch - she acts like a slacker who owes her job to nepotism, but this may just be her cover.
Big Bad Zaizen, when the truth concerning witches and humans is revealed. He goes from denial to contradicting himself, screaming louder and louder all the while... and this from a guy who was the epitome of composure the entire series.
Wham Episode: Loaded Guns. Robin is declared a witch and goes into hiding. Amon disappears and is possibly dead. Zaizen's Evil Plan is revealed.
Again in the episode where Robin is befriended by a mixed marriage of a witch and human whose innocent teenaged daughter was kidnapped by the STN-J.
Capping it off is the episode where a centuries-old witch uses an Exposition Beam to showcase just how thoroughly humanity has been persecuting the good and bad witches even long before Salem. Really, humanity got lucky that there was no Witch Magneto to lead the oppressed witches in a revolt against muggles.
"World of Cardboard" Speech: Robin says one when she discovers the secret behind the Fragment of Wisdom. "I can see it... The inner secrets of the craft... I can see his element of air. You burned the fragment to ashes. I see...This is the true craft. The power derived from the elements, lying dormant in my body, not captured in some "fragment of wisdom". That's why you attacked me. Tell me, what makes you think I am a witch?