The Great Kanto Earthquake struck on September 1 Taisho 12(1923), nine years after the completion of the No.2 Sea Fort upper structures, and three Tokyo Bay forts were severely damaged. Although the main parts such as turrets remained, the sea fort was not restored because the need for the sea fort was diminished as the performance of the artillery improved and the range increased.

And No.2 Sea Fort has been deteriorated enough to make cracks on the dome and wall of constructions and this made bunker declined forward.