Plot
Once upon a time, there was a mermaid princess called Lara. With her father, the Ocean King, and along with her loving sisters, she grew up happy and healthy.
One day, Lara fell in love with a human prince that lived on land. Such love was inexcusable and forbidden by the merfolk.
Nevertheless, Lara decided to venture into the land.
After drinking a potion concocted by the witch Grace, Lara took a human form.
However, it was a forbidden potion. If she failed to find her ＂true love＂, she would turn into sea foam.
Although she was a mermaid, Lara longed to find human love.
Alas, her wish was not fulfilled, turning into foam and vanishing in the sea.

Two hundred years later, after a long time, Princess Lara resurrected in Lake Biwa, Japan.
This time, she is determined to find her ＂true love＂.

(Source: Original translation of the official website intro.)

Story
Once upon a time, a mermaid princess named Lara fell in love with a human prince. To be with him, she used a witch’s potion to become human—but the magic came at a cost: If she failed to find true love, she would vanish into sea foam forever. Now, 200 years later, Lara awakens in Lake Biwa with one final chance at life and love.

(Source: Crunchyroll)