(cause Black Butler is awesome and should be watched)
Character Development and Dynamics
Part of what helps with anime and manga is there is a visual element, so it's a little different than writing novels in that we don't have pictures to go along with our words. But at the same time, it's kind of nice because readers can imagine the characters their own way since a common complaint when a book becomes a movie is the one playing the character doesn't look how they pictured in their own minds. We can describe to a certain degree but also choose how more or how little to give the reader. However, having a keen eye on the characters, their interactions and why those characters were chosen together for the story is one that can help us all as writers. Because who makes it into the ensemble/cast/etc does make a difference.
Romantic Pairings - Romance can be in any type of novel, not just romance books. Even epic fantasy will have some romance subplots and the pairings are important because couples forced tend to annoy readers. We have to consider what makes a couple work and how they balance each other out. Junjou Romantica is interesting, especially the main couple because it's a boy who is like 18 and a guy who is 28, which might seem creepy but they have a good balance and enough to create conflict in their story to keep things going. Pairings have similarities but also differences that counter each other. The arrogant with the lacking in confidence, the childish with the not old enough to have that maturity that age brings, etc. It's in their depth that the compatibility is created.
Ensemble Casting - Each character not only holds its own individual role but there are also dynamics that come out between each character and they should combine in ways that help the story. I recommend looking at Monochrome Factor when considering this because if you look at the group that forms, it really shows a lot and helps drive the story forward at the same time. The ensemble also comes out in Black Butler first season more towards the end, though in the beginning the ones around him don't seem all that special but man do things change later on and we get to see the truth of the characters and their roles. The main point is, consider each role when casting characters in a story, especially the ones with more stage/page time.
Another things I've noticed with anime is that the stories do a good job creating questions in the watcher's mind. There is always a number of questions brought up with each episode. A little puzzle, almost like with mysteries only some differences too, that the person watching wants to find out. Some are for the single episode and others are for the full season or show. Having someone wander something in a story is a good thing, as long as you can deliver an answer later because questions are what people remember. I had a friend read the first terrible draft of my YA mutant novel, he doesn't remember anything really, none of the character names, the story as he read the less than 23,000 words like over 4 years ago when it wasn't even finished really. But he does remember one question he had for a part near the end that I hadn't finished. That one question still is there, which shows how strong a simple moment can be in a story.
Answering Those Questions
This is one thing anime isn't always good at, nor are tv shows in general that I've noticed. While they answer the main questions there are times when an episode poses a question but the answer never gets exposed. Try not to do that when writing.
If you reveal a character has a dark secret... then let us know what it is. Yes, Monochrome Factor, I'm looking at you with this. Don't say the main character has a big secret that none of the friends know but they pretend to know to exploit him to do what they want then never in the rest of the series show what the secret the character worked so hard to keep from having exposed. People want to know his secret. And if it's not what I think it is, umm too bad, I'm going to make fanfiction (and I don't ever write fanfiction) and pretend like it was whatever I'm thinking cause you won't tell me.
I get that tv shows can't go back to every bit they ever run but if you really look at series and some of the episodes you find will just bring up a big issue and we never hear about it again. Two and a Half Men, you do this all the time and it bugs me.
So, for novels, try not to do that if you can. Plus, you never know all the work in a series you are putting yourself into when creating many threads that have to be tied up by the end. I can imagine that Brandon Sanderson had his work cut out tying things up with the Wheel of Times series because all those massive books created so many story threads it was literally like that thread thing they talk about in the story, ironically enough.
If you have never watched anime before, try out a couple episodes. You might learn something. If you already watch anime, now you have an excuse because you can call it research. ;-)
Do you watch anime?
If so, which ones?
Do you know of anything else a writer can learn from anime?