Mermaid Sisters (Japanese: マーメイド・シスターズ ) is an acapella group who participated in Mars' Brightest. They are quadruplets.
The Mermaid Sisters are buff, yet skinny, with black dreadlocks tied into braids covered by bright blue wigs, they have mustaches and a single strange of hair on their chins. Three of them wear pink dresses, tied with a red ribbon and white corset, while the fourth sibling performs shirtless with baggy pants.
They have no real personalities, despite the fact that they get angry when people insult their song.
They appear as contestants for Mars' Brightest Competition. In the first round, they faced GGK. When they came on the stage they explained their "Mermaid Sisters" name come from they not being female, nor male and that mermaids are neither human or fish, so they want to became a new race, the Mermaid Sisters. Then they started singing their song "The Mermaids of the Galaxy".
While performing everyone was shocked due to the uncensored lyrics. Catherine couldn't listen for the whole song and stopped them, announcing GGK as winner. As she told them that their song had great harmony, but bad lyrics. The Mermaid Sisters got angry, claiming that the lyrics are the true words for them and attacked the jury table.