Princess Shirahoshi, famous in the world as the Mermaid Princess, is a giant smelt-whiting mermaid and the princess of the Ryugu Kingdom, as the youngest of King Neptune's children and the only daughter in the Neptune royal family. She’s also Zach Loud’s giantess big sister and loves him very much like her mom and big sister in a blender mixed together and hoping to have him back home if he decides to be with her.