Raki, Aine and Mio pass through another door and end up on a ship in the middle of the sea, with Ichigo unexpectedly following them. The four idols are suddenly apprehended by the ship's crew and locked up. But luckily Raki's sister Saya shows up to help them escape and gives them disguises. Saya informs the idols that they are on an idol school ship called Neo Venus Ark and that she is researching idol pirates. Raki pushes Saya to explain more about her Aikatsu pass but all Saya says is that the 'experiment' is entering its final phase. The idols are caught again and brought before Elza Forte, the proprietor of the ship and a top idol, and Ichigo discovers that Mizuki Kanzaki and Mikuru Natsuki are aboard too. Elza decides to make things interesting and has the idols compete against each other.
ネオ・ヴィーナスアークで、不審者として捕らえられてしまったらき達。
そこには、“アイドル海賊”の噂を聞きつけたさあやも乗り合わせていた。この船を降りることを条件としてレジェンドアイドルとステージ対決をすることに……！？
