Château de Tsumurizaki, Mountain fortress in Hiroshima, Japan.

Kashirazaki Castle (Tsumurizaki) is a mountain castle on Mount Kashirazaki, 504 m high with a 200 m relative height, in the Aki province's Takaya area, now part of Higashihiroshima. Its enclosure spans 900 m east-west and 600 m north-south, with earthwork baileys such as Kō-no-maru, Nishi-no-maru, Taiko-no-dan, Enshō-no-dan, Keikoba and Taishō-jin.

In 1523, Hiraga Hiroyasu built the castle on Mount Kashirazaki after the fall of Kagamiyama Castle, installing his son Okisada as lord. Okisada sided with the Amago clan against his father, and in 1540 Mōri Motonari took the castle for Ōuchi Yoshitaka. After the 1551 Taineiji Incident, Mōri attacked Hiraga Takanobu and gave the headship to Hiraga Hirosuke. The castle was abandoned in 1600 when the Mōri moved to Chōshū.

The castle's name comes from Mount Kashirazaki, where the ruins stand at 504 metres. The grounds keep the names of their baileys: Kō-no-maru as the main enclosure, Nishi-no-maru, Taiko-no-dan, Enshō-no-dan, the keikoba training ground and the taishō-jin command post. The site is protected as part of the "Hiraga clan ruins", designated a prefectural historic site on 28 April 1969 together with Misonou and Shirayama castles and the Hiraga cemetery.

Visitors reach the castle through a steep forest path that requires proper hiking shoes and water supplies for the journey. Plan for a moderate climb with adequate time to explore the ruins and enjoy views from the hilltop position.

The castle's main enclosure, called Kō-no-maru, sits on Mount Kashirazaki at 504 m, with a relative height of about 200 m. The site spans 900 m east-west and 600 m north-south, making it one of Hiroshima Prefecture's largest castles after Yoshida-Kōriyama. Earthworks of the Nishi-no-maru, Taiko-no-dan and Shōen-no-dan enclosures remain visible along the ridge.