The Demaru is the only singular section out of all the defensive circles that is arranged to point out to the western side. Its position is believed to be the origin of its name.
In the records, it’s written that originally, there was a 22 meter long wall with a stone foundation from the Ninomon Gate to the Demaru. The records also state that the width from east to west was 24 meters, and the length from north to south was also 24 meters. There were only two exits to the Demaru; the path behind this stone foundation, and in the very back on the right side. If you took the exit on the back right, it would take you on a path around the stone foundation of Honmaru.