Kai, a young middle schooler, lives in Hinashi Town, a lonely fishing village, with his father and his grandfather, a sun-umbrella maker. He used to live in Tokyo, but after his parents divorced he moved back to his parent's home town. Kai has trouble telling his parents the complicated feelings he has for them, and he's lonely and pessimistic about his school life. One of his joys is uploading songs he writes to the internet.

One day, his classmates Kunio and Yuuho invite him to join their band, "SEIRÈN." As he reluctantly follows them to Merfolk Island, their practice spot, they meet Lu, the mermaid girl. Lu sings merrily and dances innocently. As Kai begins to spend time with her, he starts to be able to say what it is that he's really thinking.

But since ancient times, the people of Hinashi Town have thought that mermaids brought disaster. Something happens that puts a huge rift between Lu and the townspeople. And then, the town is in danger. Will Kai's cry for the heart be able to save the town?

(Source: Fuji Creative Corporation)

Takes part a while after Ikki accepts Simca's offer to become the new leader of Genesis. Shows the Battle between Kogarasumaru and Potemkine. The episode takes place between episodes 21 and 22 of the main series.

The continent of Atlatan once again finds itself devoured by the flames of war after a horrific event known as the Great Hall Tragedy. What was supposed to be a joyful occasion that would establish peace between the Fantasia Union and the Factory Alliance, the marriage of Sir Alexis Douse and Lady Marrine Kreische, was instead a tragedy. As the bride and groom walked down the aisle, the ceremony was suddenly interrupted by a powerful convergence of "Chaos," a dark energy from another dimension that corrupts the land and brings forth monsters and demons into the world. From within that energy appeared the Demon Lord of Diabolos, an evil being who instantly murdered the archdukes of both factions, shattering any hope for peace between them. Having failed to prevent this disaster, Siluca Meletes, an Alliance mage, is traveling through the Chaos-infested countryside to study under a master magician. When she is intercepted by a group of soldiers working with the Federation, Siluca is rescued by Theo Cornaro, a young warrior carrying a mysterious "Crest," a magical symbol that gives its wielder the ability to banish Chaos. Bearing no allegiance to a specific domain, Theo hopes to attain the rank of Lord so that he can liberate his home town of Sistina from its tyrannical ruler and the Chaos spreading within it. Impressed by his noble goal, Siluca enters into a magical contract with Theo, and the two embark on a journey to restore balance to their war-torn land. [Written by MAL Rewrite]

It is said that every few years, there is what's known as the "Summer of Anu." During that summer, thanks to the divine protection of the sky-god Anu, all of the demons in the tower lose their power. The country of Uruk has begun an invasion of the tower in order to suppress the demons. They've built up positions inside the tower, with their sights set on getting to the upper levels. The Uruk army knows that this is the third Summer of Anu-a perfect time to launch a mission to suppress the monster Druaga once and for all. The army soldiers aren't the only ones in the tower, though. An enitre city called Meskia has formed inside the tower's first floor. It plays host not just to soldiers, but also to adventurers who have heard rumors about a legendary treasure called the Blue Crystal Rod, which is said to rest at the very top of the tower. With all these different groups in the mix, each with its own agenda, one can only guess how things will play out during this unusual summer. (Source: Newtype Magazine)