Three years after an accident that nearly left him for dead, Tomoharu Natsume is about to start his high school life. Though with a ghost named Misao following him around, Tomoharu is far from being an average teenager. One day a strange woman appears and gives him a trunk that contains a tremendous power. This power is known as an Asura Machina - a being that draws its strength from a human sacrifice - and the sacrifice within Tomoharu's Asura is none other than Misao. As the bearer of such a power, Tomoharu immediately becomes the target of various groups, including the Divine Guards, who want his power for their own. When Tomoharu befriends a demon called Kanade and she is captured by the Divine Guards, he joins the Dark Society in order to save her. Now, Tomoharu will have to fight alongside the Dark Society while he tries to find a way to save Misao and bring her back to life.
Kagura and Yomi are two girls who have a bond that cannot be broken. While once they fought side by side against the supernatural forces that threaten the planet, fate had something different in store for these star-crossed companions. Yet to understand the present, one must first experience the past – a time before Kagura’s involvement with the Supernatural Disaster Prevention Agency. Always cheery and good-natured to a fault, the young Kagura first meets Yomi when she is invited into her home. Over time, the two battle malicious spirits and grow closer together – but soon, more terrifying foes begin to reveal themselves. A swarm of glowing blue butterflies and a mysterious stone are harbingers of darker things to come, and one thing’s for sure: Kagura and Yomi will never be the same.
They're both about fighting demons with some crazy weapons, but Ga-Rei -Zero- is much more cruel and dark.
In both Asura Cryin' and Ga-Rei Zero, the protagonists (Tomoharu and Kagura, respectively) find their family members too busy with their own lives, and end up forming arguably stronger bonds with a few close friends. Both Tomoharu and Kagura possess great power and use it to fight evil, although Kagura is more aware of her situation compared to Tomoharu, who is ofen baffled by whatever fiasco in which he finds himself.
Ga-Rei is darker by far, but the protagonists in both series must struggle with difficult choices involving whether to fight and whether their friends are worth sacrificing for the greater good.
Each of these series rely heavily on super natural occurrences, action, and difficult decisions. The main character in each series sees little of their family and inherits something like a burden from them. That aside, Ga-Rei Zero is a darker (and better, in my opinion) of Asura Cryin'.
Years after having been exiled from the Kannagi household for being unable to utilize their fire magic, Kazuma returns to Japan, only to discover that the Kannagi family's very existence is threatened. Unknown to them, during his absence, he had become a Contractor and thus acquired a vast strength in wind magic. Not showing any remaining contempt for them, he offers to help solve the Kannagi household’s problems in return for large sums of money. Together with his younger brother Ren and the feisty heir to the Kannagi household, Ayano, he fights to protect those he cares about... for a price!
Both anime revolve around supernatural fights, and both have hot, demon (or just demon-like) and fire-related girl which sticks with main protagonist.
Each of these series revolve around super natural battles taking place, often. Beyond that, they both have a bit of fan service and leave some large questions unanswered. Beyond that, it is just a gut feeling that someone that would like one would enjoy the other.
For the main part both series resolve around supernatural battles that occur throughout the series. In addition both series feature a lead female who wields fire as their weapon though actually both females also use swords of fire. Also by the end of both series there are some largely unanswered questions but some of which do get answered by the end of the second season of Asura Cryin'. Include some lite fanservice for both series and I'm pretty sure that if you liked one then you'll probably like the other.
Touma Kamijo's right hand has the ability to nullify any form of supernatural power, whether it be magical, psychic, or divine; he lives in a city populated by students with these powers. Yet unfortunately for Touma, his arm also seems to nullify good luck. Despite his bad luck, the boy tries to stay out of trouble and just live out his life, trying to be the "good guy" whenever he can; but trouble enters his life one day when he finds a young girl hanging on his balcony. She turns out to be a nun of the Church of England, bearing the Index-Librorum-Prohibitorum - a collection of 103,000 forbidden texts, and as a result has a number of people after her. How far will Touma go to protect his new companion from her pursuers?
The main protagonists just keep going into fights for the sake of their dear female friends. Both series has supernatural elements and wonderful art.
Both of these series have a mixture of "science" and occult happenings with a large cast and a great number of fights.
Both series feature a good mixture of science and things of the magical/supernatural element. Granted that Asura Cryin' is a bit more about the fighting between mecha and To Aru Majutsu no Index is more about the fighting between individuals with special powers both series do a good job in keeping a good balance of action, comedy, and some romance. If you enjoyed one then your almost likely to enjoy the other.
In Amberground, the land of eternal twilight, Letter Bees and their dingos – creatures trained to protect them – deliver mail to the general populace. However, unlike normal mail carriers, their job is perilous as they must traverse the country while fighting off the giant armored insects known as Gaichuu. One day, a Letter Bee named Gauche collects his latest delivery: a young boy named Lag Seeing, whose mother was taken under mysterious circumstances to the capital of Akatsuki. As the pair travels together, they strike up a friendship, but when they finally reach their destination Lag and Gauche part ways. Now, several years later, Lag is about to take the exam to become a Letter Bee himself so that he can meet with Gauche again and find out what really happened to his mother all those years ago. But before any of that, he must find himself a dingo...
Each series is centered mainly around younger kids and supernatural events. Also, each of the main character fight with their familiar. Finally, they each have a final episode that sets up a lot of the next series quite well.
Probably the biggest similarity between the two is that they both feature main characters who tend to rely on other characters in the series to help them out and get them out of trouble. Though when the time comes they can fight for themselves. Also at the end of each series they both create a nice setup to lead into the next season.
Guided by a star only they can see, a group of maidens known as HiMEs have begun to gather at Fuuka Academy. These young women have been endowed with dangerous supernatural powers that they can use to their heart's content, but there's a price: to wield them, they must put their most important thing on the line. Now, in the midst of school work and friendships, they find themselves caught in the midst of strange conspiracies seemingly related to the terrifying monsters that attack them. Is the power of the HiMEs strong enough to save themselves and the ones they love?
Both of these anime's put their own twist on the mecha genra. The mech may look just like any other giant fighting robot, but they both have their own unique spirital side. Both of these anime's also give ample fan service. So if you want to see some big breasted women and mech that aren't just mindless robots these anime's are for you.
These series are both have a decent amount of mechas, but not the traditional version of them. They also have a decent amount of humor, action, and some sort of occult happenings in them. Finally, they both manage to put in a decent amount of fan service, if that's what you're looking for.