Since 1882, the Tokyo National Museum has stood in Ueno Park, the former grounds of the one sprawling Kan’ei-ji Temple complex. Much of the temple was destroyed during a civil war following the fall of the Tokugawa Shogunate, giving way to Japan’s first public park.

When the museum was established, most of the temple’s property that remained was moved to a new location. Now, surrounding the museum building is a beautiful Japanese garden with five historic teahouses preserved on the site. Also, half a dozen tombstones stand by the leafy path for some reason.

The graves belong to the Arima family, a samurai clan that once ruled the Maruoka Domain of Echizen Province. They must have been buried in the cemetery of Kan’ei-ji, that much is for sure. But why did they stay in the museum after all the other tombstones were removed from its premises? It's a mystery no one seems to know the answer to, not even the museum itself.