There has been explosion coming from Inkopolis, and there came a portal. The Splatoon Idol Girls were sucked in, and they were in an intergalactic dimension. And they have come across the Sailor Guardians, who turned out to be Yanderes who don't care about their duty to protect their world anymore, and also think the Splatoon Idol Girls don't care about Yanderes' rage, hate, and deceit.