The town of Seino was near Edo and was the only safe place for people in whole of Japan, for the humans entering and exiting the town were closely observed not to tell the inhabitants of the country's condition. Only some families were allowed to live their happy life of ignorance in Seino. When the Noahs weren't on missions, they would jump over to the town to lead their so called social life.
The streets of Seino had nothing to do with the traditional Japanese pavements of that time period. They were more like the European boulevards and the style of clothing of the towns people was like that of London's citizens. Phaetons were rushing up and down the streets of the town, which was not small at all and had a lot of bars, taverns, lodging houses (which were almost empty, for the lack of outside people in the town), etc.