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.
Even though Romeo and Juliet is not a movie it still has the same storyline. The Sea Prince and the Fire Child is about two creatures from different worlds who are suppose to despise each other. They then meet and fall in love. Same goes for Romeo and Juliet they are two lovers from families who are enemies. Both of these animes end the same way. They also have other similar features. For the most part it is the storyline.