In the Edo Period, Obama Castle was built on a beach called "Unpin."

Unpin Beach was once an important port of call for Kitamae-bune ships and must have been essential for the unification of Japan during the Edo Period. Tadakatsu Sakai was the elder statesman of the Obama clan at the time and eventually became the clan lord. The Obama clan had deep trust and confidence in the Sakai family, seeing as they ruled until the end of the Edo Period through various hardships.

As mentioned earlier, Furukawaya was highly trusted and depended on by the Sakai family, so much so that they often visited the guest house Goshoen, and Furukawaya went as far as to supply the feudal lord with cash when necessary. This relationship continued until the very end, and as a result, they were forced to sell their ships to support the clan's finances, and went out of business.