Ritsuka has nowhere to run or hide. He lost his memories and his mother’s loving support, and then his brother -- his sole defender -- was brutally murdered. He is entirely alone until Soubi appears, saying the words he most wants to hear, but refuses to believe: “I love you and will do anything for you.” Flung into a world of intrigue and magic, where bonded pairs battle and only Soubi can fight for him, he struggles to find his brother’s killer. Yet he must also face the most bitter question of all: if you can't remember who you were, does that mean you don't know who you are?
Naruto Uzumaki is a young ninja who bears a great power hidden inside him, a power that has isolated him from the rest of his village. As such, his only dream is to become the Hokage - the most powerful ninja, and leader of the village; but first he needs to graduate! With his inability to perform even the most basic ninja techniques, it seems that all Naruto has going for him is his determination to succeed no matter what. Teamed up with the genius Sasuke, book-smart Sakura, and their team leader Kakashi, Naruto embarks on his quest to become the Hokage. But with outside forces posing a threat to the entire Hidden Leaf village, Naruto discovers that he must become much stronger if he ever wants to realize his dream and protect the friendships he's forged.
On the eve of nobleman Oz Bezarius's fifteenth birthday, he and his loved ones gather to celebrate in a coming-of-age ceremony. But after Oz steps under a long-stopped clock and the hands finally move once more - thus fulfilling a mysterious prophecy - he is violently thrown into the legendary prison known as the Abyss by three cloaked intruders. Existing in another dimension, the Abyss is home to lifeforms born within its walls known as Chains; these beings can only live in the real world if they make contracts with humans, binding their power to the person's body. However, there's a catch - in time, the human will be overcome by the Chain's power and then thrown into the deepest level of the Abyss. When Oz wakes up in the Abyss he is quickly attacked by hungry Chains, only to be saved by one named Alice - a Chain who appeared just before he was thrown into the prison. Together, the two make a contract and return to the real world, where they are enlisted into the Pandora organization - a group researching both the Abyss and the trio that threw Oz into it. Along with members of Pandora, the duo searches to find Alice's lost memory fragments that are scattered throughout the world, to discover the secrets of the Abyss, and to determine if there's a way their contract can be broken without killing either Oz or Alice.
Pandora Hearts is a shounen whereas Loveless is shounen-ai, but if you like the idea of two people teaming up to fight magical/supernatural battles (where one of the characters is a tsundere), with a plot that's heavy with mystery of one, you're bound to like the other.
Fumihiko Matsumaru is a salary man who works in the marketing department of a snack company. As a bachelor, he tried to date a girl from his company; but coincidently, he met Aka Onda, a rookie voice actor, instead. Through another stroke of fate, Aka’s house burned down that very night. With nowhere to stay and no family to aid Aka, Fumihiko took her in; and the next day, Fumihiko’s new marketing idea was accepted, and Aka’s being hired for the product’s voice actor! As the relationship of Aka and Fumihiko deepens, the more difficult their relationship becomes. Can they live together under the same roof while keeping the secret of their relationship safe?
Looking past the typical shounen-ai recommendations, I would say that two very different shows go perfectly hand in hand.
Loveless does have "boy love" in a fantasy world, whilst Rec deals with a male/female relationship in a more real Japan. But look further than the surface, and you'll be rewarded with a rich story of true love and the struggles of coming to terms with it.
Be it Ritsuka and Soubi, or Aka and Fumihiko, you will fall in love with both couplesand want them to find true happiness.
Sakai Yuuji thought he was a normal high school student, until one fateful day when time stopped. Watching in horror, he witnesses a monster devouring the "frozen" people around him; but luckily for Yuuji, he is saved by a sword-wielding red-headed girl that calls herself a "Flame Haze". The girl informs him that he has been dead for some time now and that his current self is merely a replacement for the human that he used be while alive. He is, she says, merely a torch whose life will come to an end when the blue flame in his chest ceases to burn. After this rude awakening, Yuuji realizes that he is able to see the flames of life in other "torches"; and after discovering that a friend of his is also a torch -- and her life is burning out faster than his – he gains the courage to live out the rest of his life with meaning. Will Yuuji be able to find his place in the world before he ceases to exist?
In both series you will find a boy who is pulled into a magical world that he never new coexisted along his own. Both Loveless's Ritsuka and Shakugan no Shana's Yuuji fight for the answers they so desperately desire. I just got a sense of familiarity when watching both that reminded me of the other. Some of the familiarity came from the fact that both anime fade in and out of serious-mode to comedic-mode. They also have the protagonists attempting to lead a normal school-life while balancing the magical world.
If you are a romantic and enjoyed one for their romance qualities, you should enjoy the other. Shakugan no Shana's Shana and her feelings for the lead protagonist is a lot like Loveless's Ritsuka's situation with his lead protagonist. They both seemingly fall in love, but they deny their feelings for various reasons (Shana, because Flame Hazes aren't supposed to love and Ritsuka because he feels he is to be unloved).
Now, Loveless is Shonen-ai and Shakugan no Shana is, well, not. They still share many similarities, and I think that if you enjoyed one you should enjoy the other nonetheless.