Marin's certainty that she can fix Kanon's heart gets complicated fast, the way good magical girl shows know that meddling costs something. Urin breaking that seal wasn't an accident, it was the show proving that even pure intentions have weight in the world. This special exists because the story wasn't finished asking what happens when you decide someone else's love is yours to repair.

Marin and her friends return for one more chapter of their story between the sea and the land. Twelve months after the main series ended, the girls have gone on with their lives. Kanon now knows what she wants to do and hopes to study the ocean for a living. Beneath the waves, Marin and her group find a baby sea cow that has lost its mother, and they try to reunite the pair. The single extra episode blends comedy, fantasy, romance and magical girl elements.