Nanoha used to be a normal grade school student until one day she found a ferret in the woods -- but he's no ordinary ferret! His name is Yuuno, he hails from another world, and he needs Nanoha’s help to complete his mission: to capture the Jewel Seeds (mysterious stones that imbue their wielder with great power) that fell to Earth. Along with Yuuno, Nanoha must now collect the Seeds and protect her world, but she isn’t alone. A rival is also trying to collect the Seeds for an unknown purpose, and only Nanoha has the power to stop her…
Both involve seemingly normal elementry school girls through random chance gaining the ability to use magic, having to collect certain dangerous items, etc. They also both have intelligent magical devices that help them along the way.
Both shows are also spin offs which veered into the magical girl genre, while their prequels were of a much different setting. Such as the main characters not being the main characters of their parent shows, very different plots, etc, save for the fact that magic existed in the Fate/Stay night and Zero realms but Triangle Heart had no magical characters.
So if your a fan of shows with magical girls, magic, or even their parent/spin offs. It'll be worth your time to atleast check it out.
Let's begin with the obvious; Both are magical girl spin-offs of very non-magical girl shows.
Other than that, both mix light-hearted elements into a more action styled show. The main objective of both heroines is obtaining several objects of magical power, as well as to befriend the other magical girl in the series. Furthermore, in neither show does the main character have an initial interest in becoming an magical girl other than wanting to help out.
If you like one you should try the other.
Sakura Kinomoto never imagined that by opening a book in her father's library, she'd be responsible for releasing wild magic into the world, yet that's exactly what she did. Too powerful to be let loose on the world, the magical Clow cards were sealed away long ago by their creator, Clow Reed. But all is not lost, for the guardian beast, Keroberos, was sealed along with the cards! Can Sakura, with the help of Keroberos, retrieve the cards before they wreak havoc on the town?
Both are magical girl shows with more classical mages and fantasy themes in the background, as well as the gathering and usage of magical cards. If you liked the more comedic, classical aspects of Fate/Kaleid Liner Prisma Illya you will enjoy Cardcaptor Sakura.
One night, Madoka has a terrible nightmare – against the backdrop of a desolate landscape, she watches a magical girl battle a terrifying creature, and lose. The next day, the teen's dream becomes reality when the girl – Homura – arrives at Mitakihara Middle School as a transfer student, mysteriously warning Madoka to stay just the way she is. But when she and her best friend Miki are pulled into a twisted illusion world and meet a magical creature named Kyubey, the pair discovers that magical girls are real, and what's more, they can choose to become one. All they must do is sign a contract with Kyubey and agree to fight witches that spread despair to the human world, and in return they will be granted a single wish. However, as Homura's omen suggests, there's far more to becoming a magical girl than Madoka and Miki realize...
Both are magical girl shows with actually dangerous villains, bringing in a horror element to the mix. However, both still contain the message of the importance of friendship that is a staple of the genre. Puella Magi Madoka Magica is darker with more sci-fi elements, but if you like one you should stand to check out the other.
Once there lived an eccentric author called Drosselmeyer who wrote grand tragedies - one of them was the tale of a prince who sealed away an evil raven by breaking his own heart into tiny pieces. However, before the story could be completed, the author died and the tale took on a life of its own. Now, in a town where fiction and reality meet, the story continues on its tragic course with Ahiru, a duck who transforms into the beautiful Princess Tutu in order to restore the prince's heart. But will Ahiru's act of love be enough to defy the story's terrible destiny and lead to a happy ending?
Both are magical girl shows with a gotta-catch-em-all plot.
Furthermore, they have about the same blend of cynicism and idealism, where horrible, horrible things may happen – but that doesn't stop the heroes from pulling through in the end, or sillier moments to take place.
Both have protagonists who only get involved in the plot due to a desire to help out.
If you like one you can certainly stand to try out the other.