Toba Castle, Coastal fortress in Toba, Japan.

Toba Castle is a hilltop fortification on the low hill behind the Toba Aquarium, overlooking Toba Bay. Its surviving stone walls are built of irregular grey and brownish rocks fitted tightly without visible mortar, rising from a paved road along the base. The honmaru site became the playground of Toba Elementary School, and the stone walls of the honmaru and the former chief retainer's residence remain.

The castle was built in 1594 by Yoshitaka Kuki, a naval commander serving under Toyotomi Hideyoshi, and functioned as a strategic maritime defense point. It remained operational until 1871, when Japan's modernization led to its abandonment.

The castle earned its name 'Two-Color Castle' from the contrast between its black sea-facing walls and white mountain-facing walls. This deliberate color choice made the structure appear visually distinct depending on where one approached from.

The site is reachable on foot from Toba Station and offers well-preserved stone walls to explore. Wear sturdy shoes since the terrain is hilly and some paths have steep sections.

The main gate opened directly onto the sea, making this one of the rare Japanese castles specifically designed for naval operations. This design reflected its specialization in maritime defense rather than typical mountain-based fortifications.