[1] During the Edo period, it was the headquarters of a junior branch of the Sakai clan, who were hereditary daimyō of Obama Domain under the Tokugawa shogunate.

At first, Takatsugu moved into Nochiseyama Castle, the ancestral seat of the Takeda clan, which was built on a mountain overlooking the city of Obama.

However, he quickly decided to build a new castle on a river delta in Obama Bay, which would give him greater control of the jōkamachi and the strategic port.

The Sakai clan continued to rule from Obama Castle for fourteen generations over 237 years to the end of the Edo period.

[2] Obama Castle was built on the shores of the Sea of Japan, on a needle-like peninsula formed by the Kita, Tada, and Minami Rivers, which contribute greatly to its natural defences.