A few notes about the Old Ryogoku Kokugikan 旧両国国技館, current site of the Ryougoku Sumo Hall (Ryogoku Kokugikan 両国国技館) (map).

The old structure was used for sumo tournaments when it was originally constructed in 1909. During World War II it was used by the Japanese military to make balloon bombs, known as Fu-Go ふ号[兵器]. In 1945 the building was requisitioned by the GHQ (Allied powers) and renamed “Memorial Hall”. In 1958 it was assigned as  Nihon University auditorium 日本大学講堂.

Old Ryogoku Kokugikan, as seen in 1932 (source):

Old Ryogoku Kokugikan Tokyo 1932

Old Ryogoku Kokugikan 旧両国国技館 after WW2 Tokyo air raids (source):

Old Ryogoku Kokugikan Tokyo air raid

Old Ryogoku Kokugikan, as “Memorial Hall” during the Occupation: