A Portuguese merchant ship arrives in Sengoku-period Japan carrying a cargo of matchlock arquebus rifles for Oda Nobunaga. During the inspection, an Oda soldier discovers castella, a sweet bread brought by the crew, and immediately presents it to Nobunaga. Impressed by the foreign confection, Nobunaga orders the merchant to stay at the castle for over a month to establish local production, treating him with high hospitality while his army trains extensively with the new firearms.

As the merchant settles into his quarters, an 18-year-old Japanese woman named Reiko arrives, sent by Nobunaga. Revealing herself completely, she explains that she was sent to keep him company during his stay and expresses a strong, open attraction to him and his world-traveling background. Kneeling before him on the tatami mat, she invites him to intimacy as the distant sounds of matchlock drills echo outside the castle.