Lucius, a Roman architect, faces criticism for his outdated thermae designs. Feeling overwhelmed, he seeks solace in a local bath to gather his thoughts. Yearning to relive the Rome of yesteryears, where one could unwind without the disruption of merchants and boisterous patrons. While immersing himself into the water, Lucius is unexpectedly sucked into the drainage below and emerges in modern-day Japan, 1,500 years into the future. Gasping for air, he encounters a group of foreigners with peculiar bathhouse customs. Pressured to modernize by his peers, Lucius decides to incorporate these customs into his designs, and thus Thermae Romae - the most favored new bathhouse in Rome - was born.
