Book Ends — The opening and closing sentences are almost exactly the same, except for Himei's age.
That and the reason why she's 'very tired'. In the opening, it's the weariness of having the fate of the world on her shoulders for far too long. In the closing, she just didn't get enough sleep the night before.
Card-Carrying Villain — Deconstructed, as being pure evil makes the Yamiko incapable of plotting and scheming.
Argon plays it straight, largely because he's Genre Savvy enough to know he's a Card-Carrying Villain and plan for it. Averted by Cobalt, who keeps his CCV tendencies in check in the interest of making his plans work.
Catch Phrase — "This should not be happening"; Himei also grimly quips that "I'm very tired" wouldn't sell any action figures. However, she gains a new one later: "I want to live."
The Chessmaster: Cobalt, the priestess, Argon. Radon tries, but is really too handicapped by his monstrousness to pull it off successfully.
Crapsack World — Sure, it's a Toyko not too different from our own... except for the presence of Yamiko, which spiritually ravage their victims, turn into their dark sides incarnate, frequently kill their original selves, and go on to wreak merry hell on the world before returning to the Yami-Gaia. That alone must mean that the rate of random, unexplained disappearances and unsolved violent crimes is much higher than our own world.
Cuckold — Seiki is forced to watch while his Yamiko rapes Himei.
Yes and no. The special finisher attacks of the Sailors instantly disintegrate any Yamiko who isn't very old or very powerful, so when the heroes plan a proper ambush or fight as a group against unskilled monsters it's over in a moment. However, this relies on the Sailor striking a pose and making specific hand motions (made difficult or impossible by injury) and going through the whole name of their attack, and the yamiko failing to get out of the way. And newborn Yamiko may not have any strength beyond that of a normal adult human with no inhibitions, but the Sailors have all the strength of ordinary little girls. Most combats are slow, unpleasant, inflict lasting harm on the heroines, and several would have been lethal without the timely arrival of assistance.
Dangerously Genre Savvy: Argon, who not only knows that he's both The Dragon and a Card-Carrying Villain, but is able to avert Smug Snake status because of it: he knows he's an arrogant, condescending bastard and plans for it. He's also aware he's in a deconstruction of the Magical Girl genre, knows the roles the others are playing and works with it.
A Darker Me — The Yamiko are the physical manifestation of this. They're just like regular people, but with absolutely no inhibitions or moral concerns. This is the clinical definition of psychopathological behavior. Robert D. Hare, Ph.D., the foremost psychologist currently (or maybe ever) teaching on the subject, has written or collaborated on a formidable number of texts.
In Real Life, a lone magical girl fighting monsters in an urban enviroment will quickly suffer combat fatigue and PTSD. If she can only fight the Monster of the Week instead of the monster maker, she will see the war as endless and despair.
A race that is Always Chaotic Evil wouldn't be able to cooperate and wouldn't be always chaotic evil either.
Enemy Without — Happens multiple times, each with significant plot effects.
Aki: ruins her reputation and tries to kill her. Alerts her to both the existence of the war (including Himei's involvement in it) and her own repressed feelings about her life.
Kotashi: tries to rape Shin, forever changing their relationship, and brings her a few steps closer to the Truth.
Himei: One of the most powerful Yamiko in existence, and possibly the most powerful newborn Yamiko in history. Actually tries to mercy-kill her and her friends (along with Dark General Cobalt), who barely make it out alive.
Seiki: successfully rapes Himei, which finally cracks her much-worn psyche and leads her to lock herself in the bathroom and slash open as many arteries as she can, in graphic detail. Despite this, he's the nicest Yamiko, which should tell you something about the rest of them...
Played straight with Cobalt who never really receives any comeuppance for the death and destruction he causes. Possibly justified as he turned traitor, and the war may not have ended without him doing so.
Lyrical Dissonance — One character runs right into it when he is told what the meaning of an American song he's enjoyed listening to while trying to cope with his parents' death. To little surprise, it's a song by They Might Be Giants.
To be more specific, it's "Everything Right Is Wrong Again", which is quite possibly the worst thing to have been listening to in that situation...
Komachi can mean "belle" or "town beauty". Aki in turn can mean "emptiness".
Kongou can mean the vajra, which involves symbolism for the Five Buddhist Wisdoms; one dictionary lists the word as "Buddhist symbol of the indestructible truth". Shin can (more plainly) mean truth, as well.
Seiki can mean "spirit of justice".
If you take some notice, the Nothing of the title Sailor Nothing translates as Mu in Japanese, making it Sailor Mu with a similar sounding to Sailor Moon.
Mind Rape — Thankfully, the victim tends to block the memory out. Probably closer to "Spirit Rape" anyway.
My Species Doth Protest Too Much — Cobalt and Ohta are both able to channel their Yamiko tendencies into constructive means rather than constant cruelties, and Cobalt is shown constantly annoyed by the inability of everyone else to follow their lead. As it turns out, they had unwittingly been helped in that regard.
Nice Job Fixing It, Villain — Aki's reputation being destroyed by her own Yamiko turns out to be the best thing that could have happened to her.
Magnificent Kamen sure shot himself in the foot by trying to let Himei kill herself, even if you don't count creating her in the first place due to being too indirect.
Noble Demon — Argon deconstructs the trope. As it turns out, having something resembling morality is not good for the self-image of a race of psychopaths. Even his treatment of Ami is deliberately meant to inflame the Saliors' will to destroy the Yami-gaia
Minor forms. Seiki lives alone, which he can barely stand, and Himei's parents don't notice her injuries.
"I told mom it was a fashionable thing at school now to tape your left hand."
Far worse was the behavior of Shin's parents in her backstory: although not the classical form of abandonment, leaving your daughter with a known child molester as babysitter has got to be one of the most negligent acts of parenting ever. It gets worse when you realize that he did it to others in the family, too.
Personality Powers: Himei's favored attack is called "Nothingness", Aki's is "Amazing Grace", Shin's is "Rude Awakening".
The Plan: The priestess manipulated Cobalt and Radon in the hopes of being able to stop the Yamiko. She was very weak, and her direct interactions were limited, but without her acting, none of the events of the story would ever have happened.
Pragmatic Villainy: Like all the Yamiko, Cobalt's a sociopath. However, he's also obsessed with getting things done in the most efficent manner possible, which means he has no time for rape, random murder, or any of the other typical Yamiko pursuits.
For all its grimness, however, it ultimately has a core of idealism. The Power of Friendship plays an important role in keeping the heroine together, and the key to defeating the Big Bad in the end turns out to be forgiveness.
Smug Snake: All Yamiko, except Cobalt, who's too much of a pragmatic villain, and Argon who's both high-functioning and Genre Savvy enough to know he's a Smug Snake and work around it. Radon is a particularly vile example.
Surrounded by Idiots — Cobalt. This is both during and AFTER his tenure as a Dark General. After the end of the Yami-Gaia, it's mere human stupidity bringing him down. Thankfully, Ohta's available to again bail his ass out, or the poor sucker might just get Driven to Suicide after the dog and pony show had already ended.
This Loser Is You: Shoutan Himei herself is always angstily complaining about being forced to live up to her responsibilities, even if she doesn't want to. Because of her attitude, countless others, including those who care about her, come to harm.
Those Two Bad Guys: Xenon and Neon. No one can really tell them apart, and Cobalt actually refers to them as the "WhateverOns.
Trailers Always Lie: What each Next Episode section said might not be what you should expect from the next chapter. You've been warned!
Villainy Discretion Shot: Played with. Done straight throughout most of the fic, with the vilest acts either done offscreen or quickly named with no description. Then hideously averted with Ami's fate, made even more effective by the earlier straight play.