The Melancholy of the Emperor - S1.E4

After he builds a bath using this knowledge, his invention gets round to the Emperor Hadrian. There, Lucius suddenly finds himself with a strong urge to use the toilet, however he is summoned by the Emperor and has to bear it. He is to become the Emperor's new architect but he feels he is not worthy of such an honor. Not a moment later he is sent once again to modern Japan, this time in a toilet-showroom, where he sees sea life footage from a digital TV (which he interprets as an aquarium) and a modern bidet toilet. He then uses this knowledge to create these for the Emperor.