The local speciality of this post station was an herbal medicine called "Wachūsan" which was claimed to be effective against stomach aliments.

There were five stores selling this medicine at Rokujizō, but among them, the Ōsumi family called themselves "Wachūsan Honpo" to emphasize their claim to be the originators.

The shop became famous in 1611, when Shogun Tokugawa Ieyasu complained of abdominal pain when visiting the area and recovered immediately after taking the Wachūsan medicine.

[6] The "Wachūsan Honpo" was listed in subsequent guidebooks and maps of the Tōkaidō and the medicine was a popular purchase by travelers on the highway.

In the back of the eastern portion are a number of palatial residential rooms arranged around a Japanese garden which was designed by Kobori Enshu.