Turtle trouble! It's been a year and a half since Sara's trip to the capital with Nelly and company. Sara's back in Hydrangea again, working as an apothecary with her friends and a young noble who calls himself her "fiancé candidate." One day, Nelly receives a report of something strange in the town's dungeon and goes to investigate. What she uncovers is a mysterious invisible shortcut in the dungeon's wall, through which monsters from lower floors are escaping to higher floors! The trouble only spreads when monsters begin to escape out into town as well. What's worse, one of these monsters is an enormous beast-a continental tortoise! It's time for Sara to return to her old home of Rosa...and a giant tortoise is coming along for the ride!