My train arrived, people got off and then it was announced that we had to wait while the train was cleaned.  Through the window, I saw the seats spin around slowly.  It looked like they were doing ballet, pirouetting around.  I saw no people.  I wondered if Japan had self cleaning trains.  Or were there tiny roombas zipping around the train that I could not see?  It was complete quickly and we were allowed to board the train. 

The second time I had to wait for a train to be cleaned, I did see a human walk through the train.  But, the seats did appear to dance and spin again on their own without help from the human.

So I did some googling and found these fun facts about Shinkansen cleaning:

It takes 7 minutes to clean the train – 1.5 minutes for trash collection, 30 seconds for seat rotation, 4 minutes for sweeping and wiping tables/windows, and 1 minute for a final check.

A single staff member is responsible for one carriage (up to 100 seats).

They use specialized equipment, such as a retractable broom and thermosensors to check for spills.

Unfortunately I didn’t get any photos or videos of the train being cleaned, but here is a train video and picture that I took for fun.