Shirahoshi

The Mermaid Princess (人魚姫) is the youngest member of the Neptune Family. First mentioned by Pappug, he claims he knows her and even promised to introduce the Straw Hat Pirates to her when they arrive at Fishman Island.

She has yet to make a physical appearance in the storyline and is at the moment only known by title and not by her name.

According to Pappug, Van der Decken IX started sending letters to the Mermaid Princess once a week and those letters gradually grew into packages. When he started sending threatening marriage proposals, the Mermaid Princess became so terrified of him that she couldn't ignore him anymore. This angered King Neptune and the Mermaid Princess' brothers gathered an army to find Van der Decken IX.