​In the year since the Battle of the Sanctuary, Subaru Natsuki has been busy honing his skills alongside Emilia and the other members of their merry band. Still, these peaceful days cannot carry on forever--and it is none other than Anastasia, Emilia's rival in the royal selection, who brings their respite to an end with an unexpected hand-delivered letter bearing an invitation to the famous Water Gate City of Pristella. Despite their suspicions about the sudden request, they accept and set off for the trade hub that lies at the kingdom's border. There, among the inviting canals and dazzling streets, await old friends, new faces, and a hidden menace lurking in the shadows!