Heart Crystals and Arrancars (SM/Bleach - SS arc spoilers)

[bissek]

Here's another plot bunny that needs a home. This one isn't quite as exotic a crossbreed as the others I've raised.
For the purposes of the story, I am operating under the assumption that Karakura is close enough to Juuban to make day trips from one to the other practical.
This is post Soul Society arc in Bleach, and occurs during the Death Buster arc of Sailor Moon.
Hino Rei is a Sensitive. She has honed this skill to aid in her official job as a miko at her grandfather's shrine, and in her unofficial job as Sailor Mars. She doesn't really know anyone else who is a Sensitive - her fellow Senshi technically qualify, but only when transformed - and as such she doesn't really know how other Sensitives view the world, or how they use the abilities that spiritual sensitivity brings. This ignorance is about to be shattered rather spectacularly.
One day, while walking through town (Insert plausible reason to go through town and NOT encounter another Senshi), she goes through a crowd which contains five people of Junior High school age. Suddenly, one of the boys in the group, a dark-haired boy with rectangular glasses, shouts "Look out!".
A split second later, Rei senses a dark force approaching. One of the Witches 5 has appeared, releasing a number of Daimons. Before she can call for help from the rest of the Senshi or get to a place where she can transform herself, something unusual happens. A girl with orangish-red hair touches her hairpins and a triangular forcefield appears. The rest of the group of students immediately move out and get everyone behind the shield. While Rei is being moved to apparent safety, the blond-haired boy getting her to cover is hit by an attack, and his heart crystal is separated from his body - or at least that's what should have happened.
Instead, from out of his body emerges an image of himself, dressed in a black gi, and wielding a five foot long carving knife (Aside: Zangetsu looks like an enormous carving knife. The Silence Glaive looks like a monster can opener. Ukyo has a mega-spatula. Maybe someone could make a spamfic about anime characters getting their weapons by raiding a giant's kitchen drawers? It's possible that Akane grabbed the meat tenderizer). He grasps his uberknife, er, sword, and charges to the offensive. At the same time, a dark-haired girl starts chanting, bringing out blasts of destruction, and a dark-skinned boy sprouts armor on one arm and proceeds to smash the daimons into pieces. Rei suddenly realizes that these people are fellow Sensitives - and that they've trained their abilities for use as weapons.
The daimons are rapidly destroyed. Before the Witch can flee, she is grabbed by the boy in the black gi - whom Rei realizes only she can see out of the people in the crowd. Then the boy with the glasses steps forward and asks "Where is Aizen Sosuke, and what is he after now?"
The group of students are apparently the enemies of this Aizen, and are under the assumption that the Witch is under his employ. Before they can get any information out of her beyond the fact that she isn't working for Aizen, a second Witch appears and helps the first escape. The group discusses the incident briefly, and the blond sums it up by saying "I guess we have to see if Uruhara's been hiding any more doomsday weapons in people's souls." Before Rei can decipher what this all means, the dark-haired girl walks over to the crowd of civilians and pulls out a device the size of a cigarette lighter. Rei (and everyone else) blacks out.
When she comes to, the group is gone. She also appears to have two sets of memories about what just happened. The version that included the attack, and a version in which a reckless driver caused all the damage and then took off. Everyone else seems to think the damage was done by the reckless driver, and their stories are amazingly consistent with each other.
Rei knows that the Senshi will need to know of this incident - and that she will need to figure out exactly what is going on here.
Who is this Uruhara who creates doomsday weapons and hides them in people's souls? Who is this Aizen who seeks them and what does he want with them? Who were those kids who destroyed the Daimons with such ease and they erased all evidence that they were there?
All these questions and more Rei will need to answer in order to solve the mystery and protect the general population.
...
Additional comments:
Experience with Yoruichi will make the group from Karakura unimpressed with the Mau. A non-Mau talking cat will surprise the Senshi a lot more.
Any encounter between in-uniform Senshi and Kon the Possessed and Perverted Plushie will likely end with Kon getting stomped/smacked/exorcized/blasted.
Since all of the people from Karakura have first person experience with healing spells, they would see absolutely nothing wrong with Hotaru's powers. As a Kido specialist, Rukia might even try to teach her some more tricks. If the knowledge is automatically passed on to Mistress 9, that might be a bad thing.
Aizen and Prof. Tomoe should encounter each other at some point. Whether they allie with each other or come to blows is open to interpretation. I can see Aizen wanting to use heart crystals and the Talismans to further enhance his Arrancars (hence the title), and Tomoe wanting to use Aizen's research and tools to make super daimons. The question is whether they would share or try to steal from each other.
My selection of Rei as the person to first encounter the Bleach gang was based on the fact that she would be the one most likely to be able to see a shinigami. If she could learn reiatsu techniques from someone in the group, that would be an interesting plot point.
Would Moon's healing spells affect Ichigo's inner Hollow, or Ishida's burnt out powers? It would be plausible for her to try it and see.
I have no suggestions for the lame CANON filler material called Karakura Superheroes. Kanonji is my least favorite character by a long shot and all the episodes/chapters he's been in after his first appearance are lame.

[Knight of L-sama]

Poin the first: Kanonji is cool becuase he is pure comedic relief and if they existed in the same universe Usagi would be a big fan.
Point the second: Ichigo et al are in High School not Junior High/Middle School and the Soul Society Arc occurs during the summer break of their first year.
Point the third: Are you going by manga or anime becuase if you're dealing with the manga when Rukia's present so are Renji, Ikkaku, Yumichika, Matsumoto (causing Haruka to get a slap up the head for getting distracted provided Michiru isn't equally distracted) and Hitsugaya are also present in the mortal world and Rukia's shinigami powers are fully returned, including her zanpaktou and she has achieved shikai. Not to mention the Visored are going to be hanging around Ichigo. I haven't been watching the filler arc in the anime so I can't say anything about that.
Point the Fourth: Saturn's powers would seem to encroach upon a shinigami's given the domain in which they work (Silence Glaive = zanpaktou?). How do you plan to reconcile them and how would Soul Society react to her emergence given that their duty is to maintain the balance of souls between the Mortal World and Soul Society and she has to power to destroy the world.

[bissek]

Usagi being a Kanonji fan, maybe. If Rei saw what he was doing to the ghosts, she would get SO pissed. As a trained miko, she'd have a better idea of what he was doing than he does.
Ichigo is listed as 15. He's a high school student, but my description in this plot overview was just a rough guess of somebody who doesn't know him at a casual glance.
I haven't seen the manga past volume 14 (Which is still in the middle of the Ishida/Mayuri duel). Is there a scanslation source you know about? And just because the other Shinigami are in the human world doesn't mean they're present at this particular fight.
The story would start out with a pre-Saturn Hotaru. The shinigami probably wouldn't notice her full power until she first transformed (nobody else did). And you're right, it is plausible to see Saturn as a shinigami with a glaive-shaped constant relase zanpakuto. The Silence Glaive Surprise is similar in nature to Zangetsu's special technique. Now, since Bankai increases the shinigami's power by a factor of 5 to 10, how scared should we be if Hotaru achieves it?
Half the reason the shinigami and the Quincy came to odds was because the Quincy were too entrenched in their ways before the shinigami tried to make them stop. If one or more shinigami came to know Hotaru before she came to her full power, they'd be in a position to train her in what NOT to do with it. That way they'd be able to pre-emptively keep such an incident from happening.
The real disturbing part will come from convincing Captain Kurotsuchi of the 12th that he is NOT allowed to vivisect the Senshi.
Again, if anyone wishes to adopt this plot bunny, please do so.

[Sailor Sedai (Ellf)]

bleachportal.net typically has good scanlations. Just they have a download timer.

[Knight of L-sama]

Ichigo is listed as 15. He's a high school student, but my description in this plot overview was just a rough guess of somebody who doesn't know him at a casual glance.

Still revise the age estimate up a bit. Exluding Chad Ichigo stands quite a bit taller than most of his classmates and around the mid-teens there is a tendency to equate age and height.

I haven't seen the manga past volume 14 (Which is still in the middle of the Ishida/Mayuri duel). Is there a scanslation source you know about? And just because the other Shinigami are in the human world doesn't mean they're present at this particular fight.

Then you have a problem becuase the odds of Ishida being around at that time are slim to non-existent as well. As of several chapters ago in the manga his father has restored his powers completely but only after getting him to promise not to have anything to do with shinigami ever again. Prior to that he had almost no interaction with Ichigo et al outside school hours. (And I use Manga Rain and Maximum7 to keep up to date with Bleach).

The real disturbing part will come from convincing Captain Kurotsuchi of the 12th that he is NOT allowed to vivisect the Senshi.

Actually the real disturbing part is when Usagi realises that she's allied herself with a mad scientist eqaul to or worse than Proffessor Tomoe, a bloody thirsty psychopath (complete with his own evil version of Chibi-Usa) and the other assorted freaks and weirdoes from Soul Society (Mayuri and Zaraki merely being the worst, not the only ones.)

[bissek]

The strange thing about Zaraki is that while he's definitely a psycho, the only people he fights with either attack him or are theoretically capable of defending themselves against him. While he lives for battle, it's the thrill and challenge that interest him, not the killing. He doesn't pick fights with those significantly weaker than him, there's no point. This makes it possible for people outside of Soul Society to work with him without getting too freaked out.
Mayuri, on the other hand, is total scum. If Kisuke's research results were sufficient grounds to exile him, Mayuri's research methods should be sufficient grounds to kill him on the spot. There is no excuse for deliberately blowing up your own men to disable a target - without even attempting to keep them alive. Deliberately arranging for people to die so you can vivisect their souls (what's the correct term for dissecting a ghost?) should also be considered criminal. Also, when all the loyal captains were called to confront Aizen at the end of the SS arc, he didn't bother to show up, which should have got him in trouble. Nobody in their right mind would want to work with him if they could avoid it, and when he dies, his daughter Nemu will be the only person to mourn him.
In the anime, there's a filler arc between SS arc and Ishida attempting to regain his powers (which is about vampires called Bounto, who are fascinated by Quincies, and also concerns Ichigo having trouble using Bankai in the human world. It also adds three more mod souls to the cast. I can't go into more detail as I haven't seen any new episodes since Bleach was licensed in March). Rukia and Renji both appear in the human world during this time, though the other shinigami who show up in the arrancar arc do not. Besides, even if Ishida promises to not involve himself in shinigami affairs (except perhaps in self-defense if an hollow decides that he's lunch), shinigami affairs never promised to not involve themselves with him (Such as arrancars trying to kill him). Besides, he still needs another shot at Mayuri... aiming higher this time.
Yachiru would be considered VERY disturbing by most normal people. Picture a 4-year old kid playing in the park with what everyone thinks is a toy sword. Enter monster attack. Four year old kid draws what turns out to be a real sword and hacks the monster to pieces. Splattered with blood, the child then bows to the mangled corpse and says "Thank you for playing with me!"
As for the Outers... I just finished looking over the scanslations and Matsumoto seems to have this habit of punching out people who pay too much attention to her cleavage, so Michiru might not get the chance to slap Haruka.

[Neko-]

If this ever sees the light of day, it'll be an interesting read for sure

[Saedin Casoria]

Aww... It's so cute! (Picks up the Plot Bunny) ^_^ I think I'll take it!
X_x I've actually SEEN some of the source material, moreso the Bleach then the Sailor Moon, but I can cover the difference with a fair bit of research...
(Clears throat, then adds) Assuming nobody beats me to the punch, I wouldn't mind trying this, but it will require some plottage...
Oh well, I've got time in the nights between 10:00 and when Big O comes on, should give me some wiggle-room to do some writing.