Thermae Romae (2012) on Netflix

Plot summary

Lucius Modestus designs baths in the Rome of Emperor Hadrian, and he finds the public ones crowded and shabby. While soaking in one, he drops through a hidden tunnel and surfaces in a Japanese bathhouse of the present day, which he mistakes for a bath reserved for slaves. The conveniences he tries there, from taps to chilled drinks, move him to tears, and the tears carry him back to Rome. He sets about fitting Roman baths with what he has seen. A second crossing puts him in a private bathroom, and there he meets Mami, a young woman who draws manga. Then Hadrian calls him to the villa and asks him to build a bath for the emperor.