Grace, the banished witch, gives Lara, a mermaid princess, a potion that turns her into a human.

Lara wakes up in the human world in Shiga and encounters Grace in pet fish form, kept by Mari.

Lara is curious about "school," and Mari fights her senior to participate in the next boxing tournament.

Lara convinces Mari to take her to school and meets Himeka and asks her about her "prince."