Season 1 (2009)

1. Heart of the Sea, Heart of the Sky

Two mermaid sisters, Marin and Urin, discover a ring that has fallen in the ocean and attempt to return it to the owner. However, when they find Kanon she refuses to accept the ring and throws it into the forest. Urin gets lost in the forest during a fireworks display and finds a sealed tomb.

2. Heart Of The Ring, Heart Of The Priestess

With Sedna's release, darkness washes over the island. Matsumoto, the elder sea turtle, awakens and explains to Marin that she is the Priestess of the Sea. In disbelief, Kanon runs off and is attacked by a creature of darkness.

3. Hearts Getting Closer

Kanon is shocked to discover that Marin, Urin, and Matsumoto have made themselves at home in her house. Marin poses as a fortuneteller to distract Suzuki from finding Kanon, who is hiding, and learns more about Kanon and her mysterious evil aura.

4. Heart Under Trial

Matsumoto gives Kanon a treasure map for Kagero Island, hoping that if she finds the treasure it will improve the purity of her heart. After Kanon and Marin leave, Miyako explains to Urin of a legend about a pirate's cursed treasure within the cave.

5. Heart which Conceals the Light

Amamiko Island is abuzz with activity as tourists flock to see the solar eclipse and Matsumoto fears the darkness such an event could invite. Meanwhile, the growing rift between Urin and Marin reaches a breaking point.

6. Hearts Falling

The solar eclipse blankets the island in night as Marin and Kanon search for Urin. Countless mysterious butterflies and a strange woman appear from the ocean.

7. Hearts Growing Apart

In the wake of Urin's departure Matsumoto's daughter, Ichikawa, is discovered in Kanon's house. A downcast and shaken Marin decides to return to the ocean to search for her sister.

8. Hearts Seeking Each Other

While heading back to the surface, Warin explains the nature Marin and Urin's relationship to Kanon. A concerned Kojima searches for Kanon, leading to a confrontation between her and Ooshima.

9. Loving Hearts

Marin returns to Amamiko Island in order to regain her ability to transform. Suzuki and Kojima tell Marin about how they met Kanon, and along the way comes to understand her own feelings, as well.

10. Silencing Hearts

11. Heart of Light, Heart of Darkness

12. Heart of the Island, Hearts of the People