Andersen Douwa: Ningyohime

Both films are adeptly written stories that are extremely well executed and are guaranteed to make you cry. A beautiful love story, similar to the tragedy of Romeo & Juliet (but FAR BETTER!), this film has the film quality of Studio Ghibli and a soundtrack composed an orchestrated by the Tokyo Philharmonic Orchestra. It is so beautiful that this music will haunt you for the rest of your life. I highly HIGHLY recommend this one.  

Both are fairy tale from old classics. -Blonde hair Heroine -Princes -Romance -Animal friends The two difference is that the endings 

Yoake Tsugeru Lu no Uta is essentially The Little Mermaid without the contract with the sea witch, the coming-of-age ceremony to go to the surface, the plot to murder the prince, the tragic ending, or the romance. Ok, Yoake Tsugeru Lu and The Little Mermaid aren't that simular, aside from the fact that their both about a relationship between a mermaid and a human and they take place by the sea. 

Umi Monogatari and Hans Christian Anderson's The Little Mermaid are two anime that feature mermaids into the story. The mermaid character(s) go above the surface of the sea and meet someone from the land. The ED for Umi Monogatari even features the two mermaid sisters watching a slideshow of the original The Little Mermaid fairytale. 

The Same Author; who wrote wonderful stories of both Thumbelina and the Little Mermaid Fairy Tales. -Both Female leads adventure into an unknown world. -Animal/Fish Friends help her out. -Witches in stories. -Handsome Prince -Morals are Learn as the stories goes on. Thou Thumbelina had a few small changes, elements from the story are there 

Puella Magi Madoka Magica and Han Christian Andersen's The Little Mermaid are both anime that take inspiration from the classic fairy tale made by the famous Danish author. And I really do mean classic—yes, the original story that was constantly debated and known for being very disturbing, and no, not the much lighter Disney version we've all been used to. 

Both of these anime are 70's vintage adaptations of Andersen's Little Mermaid, with style that is closer to traditional western fairy tale production than anime. 

The feel for the film, the music and even moments of the story itself feel similar to one another. They each deal with solitude and loss and finding something you have hope in.  

This is also part of the World Children's Classics series along with the aforementioned adaptation of Swan Lake, so the art style will be similar or of the same high quality. Also, this is one of the most beautiful children's stories I've ever seen adapted. Similar to World Masterpiece Theatre films (Anne of Green Gables/Heidi/et cetera) & Belle & Sebastian.  

This is also part of the World Children's Classics series along with the aforementioned adaptation of Swan Lake, so the art style and some of the music will be similar or of the same high quality. Similar to World Masterpiece Theatre films (Anne of Green Gables/Heidi/et cetera) & Belle & Sebastian. Bonus: Each film contains the metamorphosis of a girl and her journey through that process. The sound quality of this one is particularly good. 

Both could probably be concerned to be classic anime 'princess' movies that are more closer to the original story then there western counterparts