Chrono Crusade, on Fuji TV
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Caution: potential spoilers.
(aka "Chrno Crusade"). This is one of those animes that is frequently switching between serious drama, intense action, and over-the-top wacky humor (at least until the latter part of the series, when it abandons the humor). It's set in Brooklyn, New York, in 1928. (I find the setting fun a lot of the time, especially the slang characters use. Most notably "everything's Jake," meaning "cool." It's kind of easy to forget "cool" in its modern sense didn't exist until about the second half of the 20th century, but every era has had its own slang, of course.) Anyway, there's an organization within the Catholic church called the Order of Magdalene, which exists to exorcise devils. And um, this show's idea of "exorcism" is considerably different from the way the word is typically used. It seems more like the word means "killing," here.
The story focuses on Sister Rosette Christopher, and her partner, a devil called Chrono. In flashbacks we see that Rosette and her now-missing brother, Joshua, met Chrono when they were younger. Now, Rosette and Chrono are sent on exorcism missions by the head of the New York branch of Magdalene, Sister Kate Valentine. Rosette is pretty reckless and usually causes a lot of damage in the course of her assignments, which really frustrates Sister Kate (who also doesn't fully trust Chrono, being a devil). Rosette and Chrono occasionally receive technical support from Edward Hamilton (who is referred to as "the Elder"), an old coot who invents stuff for operatives to use, like special bullets to be used against devils. The main type of bullet is called a Sacred, though the Elder also made a more powerful bullet called a Gospel. It should also be mentioned that the Elder is a pervert, often engaging in lewd behavior and comments toward Rosette (as well as some of the other nuns). Another important member of the Order is Father Ewan Remington, who gets along better with Rosette than Sister Kate does. Later in the series we learn something quite interesting about him, though it isn't explained in detail, which is rather frustrating. Aside from Rosette and Kate, the only nuns we get to know at all are Claire, Mary, and Anna, who are almost always seen together. But they don't do much other than gossip.
I need to explain that Rosette has a contract with Chrono. Most of the time we see him looking more human than he does in his true form. Chrono's powers are constrained, and he can only call on them at the cost of a portion of Rosette's soul & lifespan. Normally devils obtain power from Astral Lines, energy which flows through the atmosphere or something. But... for a reason I won't go into, Chrono can no longer obtain energy that way. He tries to refrain as much as possible from taking power from Rosette, because of course he doesn't want to shorten her lifespan, but sometimes it's necessary. Aside from all that... the two of them are basically good friends (and potentially a romantic pairing), though Rosette can be kind of... overbearing. Seriously, her moods are all over the place. She's really nice and caring, but also gets mad a lot (and humorously abusive), and can be goofy, and can be a bit overzealous in her duties, and... stuff. So she's kind of a hard person to be around sometime, and Chrono's usually fairly meek around her. But like I said, they're good friends, in any event.
On one of Rosette and Chrono's missions, they rescue a young girl named Azmaria Hendrich, who is an "apostle." That is, one of several people who have each been given a unique spiritual power from God. Azmaria's manifests when she sings. Anyway, she joins the Magdalene Order, wanting to help Rosette and Chrono. She's a very sweet kid, but it can be kind of annoying how easily she gets scared or sad. After awhile, the three of them meet a "jewel witch" named Satella Harvenheit, who uses jewels to summon... things... to fight devils. Satella has hated all devils ever since one killed her family when she was a kid, so it takes awhile for her to accept that Chrono is a good guy. She also doesn't get along well with Rosette, though they all eventually become friends and allies. I should also say that Satella is quite rich, and has a loyal and kindhearted servant named Steiner, who is glad Rosette and the others have come into Satella's life.
Aside from exorcising devils, Rosette and Chrono ultimately want to find Joshua, who is also an apostle. He had been kidnapped by a devil named Aion, who wanted to collect all the apostles for his own purposes. There's a great deal to learn about Aion's goal, and the past, and... pretty much everything. Even after having seen the whole series, I'm sure I don't fully understand it. (There was a bonus feature on the DVDs I watched, called "Azmaria's extra classes," a series of eleven short segments narrated by Azmaria, in which she explained various things about the setting of the show, in the Roaring Twenties, and about all the things that were going on. It was helpful, but even that didn't make me fully understand everything.) But anyway, at some point in the past, Aion and a group of devils, including Chrono, had rebelled. They're referred to as "Sinners." Aion apparently killed a devil called Pandemonium, also known as Lucifer, as the first step toward his goal. (Though I guess "Pandemonium" also refers to Hell itself.) There's lots of stuff in the show that's rather confusing, about God and his relationship to both devils and humans. But basically, the reason there are so many devils around to be exorcised is because people had been becoming more sinful. And Aion wanted to plunge the world into even greater chaos. Or something. Anyway, at some point before the start of the series, Chrono had left Aion's group. This is sort of explained later in flashbacks, which I don't want to get into.
Anyway, Joshua was apparently under some kind of spell, so he was willingly on Aion's side. Also, he was looked after by a woman called Fiore, who he apparently thought was Rosette. Or something. Even though they look nothing alike. (Near the end of the series, we learn of a shocking connection between Fiore and another character, but I won't spoil what that's all about.) Um... also I feel like I never got to know most of the Sinners well enough. There was one I kind of liked, named Shader (though I never caught her name while watching the show, I only read it online). She was more of a goofy scientist than a fighter. Oh, and half way through the series, the main characters learn that Joshua is in San Francisco, so they travel there from New York. That's where most of the remainder of the story will take place. At this point another major character we'll see is Reverand Gilliam, who I guess was from the San Francisco branch of the Order of Magdalene. And... there are a group of devils who join forces with the Order, against the Sinners. The main one of them is named Duke Duffau. As I said earlier, the latter part of the series has very little humor, if any. Things get very dramatic and intense, and there are some major developments I don't want to spoil. So I can't really say any more about the plot, but the end... is bittersweet, at best.