Water Realm

The Plane of Water (水のプレーン, Mizu no Purēn) also called the Water Realm is a world that is never seen or ventured to in-game, but is mentioned throughout the course of Magical Vacation.

In Magical Vacation
Water People once lived in this realm until Enigmas came to wreak havoc. This caused many inhabitants to be separated across various planes.

The first instance of the Plane of Water being mentioned is when the party spots a Water People in the Plane of Light. Being a speaker of their Erimu Language, she is able to translate its words and tell her classmates about what happened to her family in the Plane of Water.

Eventually, the party can explore Akvavit Castle in the Plane of Darkness. By using the water of Kumuyamuto Desert, a group of lost Water People created the castle.

In Blueberry's epilogue segment, she goes to the Plane of Water for the sake of her heritage. She tells stories of her adventures to the Water People.