The HASHIHARA family had originally ruled a different territory, but it ended the war and established the new Hashihara castle town. Given the ensuing stability and peace in the world, Nobumasa may have attempted to create a new ideal town in this area.

In addition, it can be seen from the genealogical table that (1) two daughters of townspeople were concubines of HASHIHARA Nobumasa, which suggests that this was unlikely to have been a period with a pervasive class system; and that (2) the family name HASHIHARA was first adopted by an ancestor 14 generations before Nobumasa by taking the name of his territory, which indicates that a considerable period of time had passed since the Kamakura period, when the practice of using place names as family names began. Furthermore, the map shows that the moat and parts of the river were fortified by stone walls, a technique used from the Edo period onward.

Based on these observations, the project team assumed the map's historical background to be the mid-Edo period when MOTOORI Norinaga lived.

At first glance, one will notice that the entire town center was clearly divided by function, including samurai residences, townspeople areas, temples and shrines, and agricultural land on the outskirts, with the imperial palace where the castle lord resided at its heart.

Based on the content of the Genealogical Table of the HASHIHARA Family, residences of high-ranking samurai such as "Gobunke," "Gohokyaku," and "On'ozamurai" were located south of the imperial palace within the moat and walls surrounding the citadel area, while the residences of lower-ranking samurai were densely concentrated on its north side. The townspeople areas were located on the south side and around the imperial palace, while temples and shrines were spread out along the periphery of the town.

The actual castle town was also divided into samurai residences, townspeople areas, temples and shrines, etc., but due to constraints related to topology and existing land use, the division was not as clear-cut as it could be.

From these observations, it can be inferred that the Hashihara castle town had been meticulously planned and developed.

The Hashihara castle town was carved up using a grid layout featuring streets that stretched from north to south and from east to west, with each street given a name. Incidentally, the streets in many castle towns of the same period were not arranged in a strict grid layout. For example, the streets of Matsusaka, the hometown of Norinaga, were not set out in a grid layout, and he later indicated in his essay Tamakatsuma that "the town's streets do not look right." Also, although Kyoto, the city that Norinaga was drawn to and appeared to have used as a reference for his own town layout, features a grid layout, it also has diagonal and curved streets, and, unlike Hashihara castle town, no town in reality is actually composed of entirely straight streets.

Furthermore, maps of Kyoto at the time sometimes used different vertical and horizontal scales, depicted square districts with rectangles, and even omitted the names of streets. However, the Hashihara Castle Town Map uses the same scale in both vertical and horizontal directions and was marked with the name of every street, making it even more precise in depicting the town than maps of Kyoto at the time.

When the project team identified all the street names and compared them with those in Matsusaka and Kyoto, it was found that although several streets shared the same name with streets in Kyoto, such as Ogi-cho and Kamiya-cho, none corresponded to actual streets in Matsusaka. It seems that Norinaga had avoided the names of real towns and cities and planned a town of his own despite his strong attraction to Kyoto.

The project team performed an estimation of the town center's size and the resident population of the Hashihara castle town. The first step was to elucidate the scale of the Hashihara Castle Town Map. Only the following three distances were marked on the map:

1. ① Distance from Sugino to the Tamatarejima boat crossing
2. ② Distance from the boat crossing on the east side of Shin-sonozaki Hachimangu Shrine to the Tamatarejima boat crossing
3. ③ Length of Kasenbashi

The distances ① and ② were deemed to be not drawn to scale because there were many instances in maps of that period of distances in peripheral areas becoming less accurate the further away they are from the town or city center. Therefore, the scale of the Hashihara Castle Town Map was determined to be approximately 1/6,200 based on the actual measurements for ③. On the basis of this scale, the area of the town center was calculated to be approximately 6 km², or around 3 km from east to west and around 2 km from north to south, which is about half the size of the current Chiyoda Ward in Tokyo.

By defining each square block often seen in the townspeople area to the south of the (high-ranking) samurai residences as one district, the size of the townspeople area was calculated to be approximately 9,000 m² (around 95 × 95 m) per block, or around 50 ken when converted to the unit of length used during that period. The scale suggested that the districts had been planned to be more compact than those in Edo and Kyoto, whose layout was based on around 60 ken per block at the time. Nagoya, however, had districts with around 50 ken per block.

The townspeople areas were annotated with only the names of streets and nothing else. It was common practice to avoid annotating townspeople areas in great detail on maps of that period.

In the Edo period, districts in townspeople areas had vacant lots known as centrally owned land, where town houses were built along streets. Some districts had a road running through the center, while others had temples and shrines built on them. This is because roads, temples, and shrines were often planned on vacant lots. At the same time, it is thought that the construction of new public facilities was avoided in vacant lots within districts where influential townspeople lived.

The population was calculated by applying the average number of residents at the time to each district based on the size of buildings in general during the Edo period. Therefore, assuming that 200 to 380 people lived in each district of the townspeople areas, these figures were applied to the 220-odd districts of the townspeople areas to arrive at an estimated total resident population of 45,000 to 85,000 townspeople.

The same method was used to calculate the resident population of samurai residences. Within the citadel area comprising high-ranking samurai residences, the population was estimated to be around 8,000 people based on the kokudaka figures indicated in the family structure materials and genealogical tables for the HIKONE clan during the Edo period. For the area allocated to lower-ranking samurai, the resident population was calculated to be around 10,000 people based on the number of households in the residences listed in each plot and the assumption that four individuals lived in each household.

Based on the above, the total population of the town center of the Hashihara castle town was estimated to be in the range of 60,000 to 100,000. The project team also arrived at a population estimate of around 88,000 people by calculating the population density of the castle town based on the population of Kyoto's Rakuchu area in 1730 and applying it to the area of the map. Given the proximity of these two values derived from two different approaches, the project team concluded that this population estimate was reasonable.

In the process of estimating the population, the project team placed town houses and samurai residences of standard sizes built during that period in each district according to the scale and found that most of these buildings fit perfectly within the plots.

This suggests that Norinaga had meticulously planned the width of streets, districts, and the population, and he even accurately determined the sizes of samurai residences and ordinary houses at the time in order to plan the residential plots with precision. This map can thus be said to be an accurate representation of Norinaga's town plan.

What was the rank of the daimyo Nobumasa, the ruler of the castle town? The total kokudaka of his vassals listed in the genealogical table was 280,000 koku, and his territory was spread over 22 gun (districts). Based on this information, it can be estimated that Nobumasa's kokudaka was in the range of around 500,000 to 900,000 koku, which is equivalent to that of a daimyo of the WAKAYAMA clan that ruled Matsusaka where Norinaga lived, or the OWARI clan under the same Gosanke (three noble houses) as the WAKAYAMA clan. In terms of population, Nagoya, the castle town of the OWARI clan, had a population of under 100,000, which was roughly the same or slightly larger than that of Hashihara, estimated to be in the range of 60,000 to 100,000.

As for the location of the Hashihara castle town, it was indicated that the town was located 2.5 ri from the port, or around 10 km from the sea. Based on the direction of flow of the river, it is thought that the sea would be to the left of the map, on the west side.

On the other hand, it is unclear which part of Japan the town was supposed to be located. One clue is that coniferous and broad-leaved forests, as well as plum and cherry trees, were depicted in the mountainous areas. The simultaneous presence of these plants points to many possible regions in Japan, although extremely cold regions in northern Japan as well as southern regions of Japan with few coniferous forests can be ruled out.

In his later years, Norinaga described Ise Province, where Matsusaka is located, as being "neither too cold nor too hot as compared to other provinces," and it is highly likely he had in mind a region with such a warm and pleasant climate.