Kaiten Memorial Museum

The Kaiten Memorial Museum (回天記念館) stands on Ozushima (大津島), a small island in the Seto Inland Sea accessible only by ferry from Tokuyama Port in Shunan, Yamaguchi Prefecture. The island served as the Imperial Japanese Navy's first kaiten training base, established in September 1944.

The kaiten (回天, literally "turn the tide of heaven") was a manned torpedo — essentially a modified Type 93 torpedo fitted with a cockpit, periscope, and self-destruct mechanism. A pilot would board the weapon aboard a submarine, launch toward an enemy vessel, and guide it to impact, sacrificing his life. The program was conceived by Lieutenants Hiroshi Kuroki and Sekio Nishina in early 1944 as Japan's war situation deteriorated, and the name reflected their desperate hope to reverse the course of the war.

Ozushima had been used as a torpedo testing site since 1939. When the kaiten program was approved, the island's existing facilities — including a 250-meter tunnel cut through rock for transporting torpedoes by rail — were converted to support kaiten training. Pilots practiced navigation around the island in training versions of the weapon. Of the four kaiten bases established nationwide (Ozushima, Hikari, Hirao, and Oga in Oita), Ozushima is the only one where original facilities remain substantially intact. In 2006, the site was designated a Civil Engineering Heritage Site (土木遺産) by the Japan Society of Civil Engineers.

The museum first opened on November 20, 1968, near the remains of the training base. It was enlarged in 1988 and comprehensively renovated in 1998. The collection of approximately 1,000 items includes farewell letters, wills, diaries, photographs, uniforms, and personal belongings of kaiten pilots and maintenance crew. Exhibits include information panels on the historical background, dioramas of daily life at the base, a training room recreation, and a video corner featuring interviews with surviving former pilots. A full-scale kaiten replica, nearly 15 meters long, is displayed in front of the museum.

The island's preserved wartime remains include the transport tunnel, maintenance facilities extending from Mashima port to the former Ozushima Elementary School, an electricity transformer station, concrete bridges, observation stations overlooking the torpedo testing area, a firing test evaluation office, hazardous materials storage, kitchens, and barracks.

Approximately 145 kaiten pilots died during training and combat operations between November 1944 and August 1945. Only the Type 1 kaiten saw actual combat deployment, launched from submarines against Allied naval targets in the Pacific.