The Five Routes (五街道, Gokaidō), were the five centrally administered routes (kaidō), that connected the city of Edo (former name of Tokyo) with the outer provinces during the Edo period (1603–1868). The Five Routes were formally nominated as official routes for the use of the shōgun and the other daimyō and to provide the Tokugawa shogunate with the communications network that it needed to stabilize and rule the country.
One of The Five Routes and one of the two that connected Edo to Kyoto was The Nakasendō (中山道, Central Mountain Route), also called the Kisokaidō (木曾街道). There were 69 stations (staging-posts) between Edo and Kyoto. Prior to the Edo period, the route had been called both "Sandō" (山道 "mountain route") and "Tōsandō" ("eastern mountain route"). During the Edo period, the name was changed to Nakasendō and was written as both 中山道 and 中仙道, but the Tokugawa shogunate established 中山道 as the official name in 1716.
Originally, Honjin were places from which generals directed battles and, therefore, were fleeting in nature. However, as commanders began to transform the honjin into temporary lodgings during battle and travel, honjin came to be places where daimyō and other representatives of the shogunate, including hatamoto, monzeki, etc., were allowed to stay during their travels. Many of the honjin were actually personal residences of village and town leaders.
Waki-honjin (脇本陣), also referred to as "sub-honjin," are similar in structure and operation to, but generally smaller than, honjin. The rules of operation were also slightly different. When two official traveling parties are staying in the same post station, the more powerful of the two stayed in the main honjin. The major difference, though, is that general travelers were able to stay at the waki-honjin, if they had enough status or money.
Waki-honjin Okuya in Tsumago-juku (the 42nd post town) has been restored to its appearance as an Edo-era post town and has been on my list for more than five years. Reflecting its surrounding nature, the Waki-honjin Okuya was constructed from cypress trees of the Kiso mountains (kiso = cypress).
(the rest of the story is in comments) ...