Castle walls have recently become popular with tourists, especially rekijo (female history buffs) who like to view them even when the castle itself is no longer there.
Since the Meiji Era, however, the number of masons who repair and preserve the stone walls has been on the decline, and many walls have collapsed during disasters.
The government has set on fostering young masons and introducing cutting-edge technology to conserve castle walls, which are regarded as cultural assets.