A yakuza boss hires Goemon Ishikawa, a modern day samurai, to protect him aboard his cruise ship casino. Everything goes sideways when the famous thief, Lupin the Third, tries to rob the vessel. Lupin's being hunted by a powerful and mysterious man: the so called “Ghost of Bermuda.” With Goemon's employer dead in the ensuing chaos, his honor is at stake, and the only way to preserve it is with blood. But this opponent is like no other, and to make things right, Goemon may need to sharpen not only his sword, but himself as well!

The story follows a Roman architect named Lucius, who is having trouble coming up with ideas. One day, he discovers a hidden tunnel underneath a spa that leads him to a modern Japanese bath house. Inspired by the innovations found there, he creates his own spa, Roma Thermae, bringing in the modern ideas to his time.