This movie is "That Time I Got Reincarnated as a Slime the Movie: Tears of the Azure Sea" and story line : After concluding the opening ceremony of the Demon Kingdom Federation Tempest, Rimuru and his companions are invited by the Celestial Emperor Hermesia of the great elven nation – the Magi Dynasty Salion – to visit her private resort island. As the group enjoys their brief vacation, a mysterious woman named Yura appears. A new incident unfolds against the backdrop of the boundless azure sea..