Miho accepts her best friend's invitation to work part-time aboard the Northern Light during its celebratory 200th voyage. As the ship sets sail with invited guests only, she takes on casino waitress duties alongside a fellow student performing violin in the restaurant, an idol greeting fans on the main deck, and a professional dealer handling the tables. The initial days unfold with the promise of summer memories and new experiences at sea, yet the atmosphere gradually shifts in ways none of them anticipated.