Beyond the knowledge of most people, the world contains a dark secret: of every person in the world, there exist two identical copies (called Doppeliners) with the same body and mind. Among the three, however, is distributed only a finite amount of fortune; should they ever encounter one another, the one with a smaller portion dies and the remainder is distributed until only one, the Master Root, survives. Keita Ibuki lives his day-to-day life as ignorant of this as everyone else until he stumbles upon a mysterious young girl named Kuro who explains to him these secrets of the world. Despite not wanting to have anything to do with her or the danger that inevitably seems to follow, their fates become intertwined and he finds that the Doppeliner system has more to do with his past than he realizes.
Both series have a mysterious heroine with a strange goal, a boy who must follow her, many weak enemies, a lot of short fights and confusing storyline.
I don't know why, but when I was watching Yumekui Merry I was under the impression that it is awfully similar to Kurokami the Animation. It's possible that you too will feel the similarities.
The two series, Yumekui Merry and Kurokami the Animation, have the main theme of mystery. The goals of the main characters are not revealed in their entirety until the end of the series.
A giant wall looms over Tokyo, shielding the city from a dangerous otherworld called the 'Hell's Gate'. Within the city, things are no less terrifying because Contractors, psychopathic killers with phenomenal powers, have started to appear. These killers are compelled to pay a price every time they use their powers, often in the form of a meaningless or painful task. As their deadly habits rack up a gruesome death toll, Kirihara Misaki and her team from the Foreign Affairs Public Security struggle to solve the cases and bring the Contractors under control. Their task is further confounded by the interference of a masked individual they title Messier Code BK201, a man with abilities that allow him to fight and defeat the Contractors. Who is this BK201? How can the Contractors be stopped permanently? And what does the appearance of the Hell's Gate mean for the people of Tokyo?
Apart from having the same feel to the animation, both of these anime have similar fight sequences with very similar styles and energy. The theme of the supernatural fighter is prevalent in both as well.
The Holy Grail War is a battle between seven magicians who each summon a mythical hero to fight for their cause. Shirou, a twice orphaned high school boy, had so little magical talent that his foster father did not bother teaching him about the war and its meaning. Thanks to that lack of foresight, Shirou finds himself in a bit of a pinch when he accidentally summons a hero of the strongest class, and is sucked into the fray. The Grail grants the winner any wish they have. But driven by an unyielding sense of justice and self-sacrifice, for what will Shirou fight?
Both of these have the Master/Servant feel to them. Although the battling system is quite different, both have an ideal of a peaceful world.
The voice actor for Kuro in Kurokami is the same as Sakura Matou in Fate Stay Night. If you like Sakura (as in heavens feel Sakura, not really covered in the anime) then you will probably like Kuro as well.
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!
Whilst kurokami has the male-female pair dependant on each other, and KnS the girl aspiring to be like the male...
Both relate to fighting to keep balance in the modern world, with there existing different factions with different motives and goals.
There exists the plot-based similarities of the super-powered evil 'older brother' character, and a development of super latent powers that has to be harnessed.
Ouri is an orphan who was raised by Keisei, a man he considers to be his older brother. One night, Ouri finds a strange wounded girl in the temple of the orphanage. Cold and covered in scars, Ouri initially thinks that she is dead – that is, until a mysterious talking cat tells him that she is a Shikabane – a corpse. After secretly watching Keisei heal the girl without explanation, Ouri decides it's time to leave the nest. However, he has picked a poor time, and he soon realizes that he's tangled in a strange, supernatural web. Why does Ouri continually meet this girl as she hunts monsters? What does Keisei have to do with it all and what exactly is her mission?
Similarities is mainly that it is a male-female orphaned highschool-aged pairing to restore balance to the world after something (via some big plot/secret organisatio) has upset it. Shikabane hime is much darker and grittier.