The tomb almost certainly belongs to Soga no Umako, the most powerful political figure in Japan during the late 6th and early 7th centuries. Umako served as Great Minister under Empress Suiko and wielded authority that rivaled the throne itself. When he died in 626, the Nihon Shoki -- Japan's oldest official chronicle -- recorded that he was buried "in the tomb at Momohana." Historian and archaeologist Sadakichi Kita connected this passage to the Ishibutai Kofun in the early 20th century, and the identification has held. But the tomb's nakedness tells a darker story. Kita also proposed that the earthen covering was deliberately stripped away after Umako's death -- a posthumous punishment inflicted by the imperial government on the Soga clan, whose accumulation of power had long alarmed the court. Stripping a tomb bare was the ultimate insult: exposing the dead to sky and rain, denying them the dignity of concealment.

The 30 stones used to construct the Ishibutai Kofun were quarried from Mount Tonomine, several kilometers from the burial site. The total weight of the structure is estimated at 2,300 tons. Two ceiling megaliths are the most impressive components -- the larger southern stone alone weighs approximately 77 tons. How 7th-century builders transported and placed these blocks remains a subject of study, though log rollers, earthen ramps, and coordinated labor forces numbering in the hundreds are the most plausible methods. The tomb originally sat on a square platform surrounded by a moat, a standard feature for elite kofun of this period. A long stone-lined approach led to the burial chamber, which opens to the southwest and includes a drainage system channeling water away from the interior. The engineering reveals sophisticated understanding of both construction and preservation -- ironic, given how thoroughly the tomb was later despoiled.

When archaeologist Kosaku Hamada first excavated the Ishibutai Kofun in 1933, he found almost nothing inside. Grave robbers had likely cleaned out the burial goods soon after the earthen mound was stripped away, perhaps even while the Soga clan's political fortunes were still collapsing. What the excavation did reveal were fragments -- stone shards from a tuff sarcophagus lying southeast of the chamber, scattered gilt and bronze implements in the approach banks, and earthenware pieces. Digging also uncovered seven smaller stone burial chambers that once flanked the main tomb. These turned out to be older graves that predated the Ishibutai -- tombs that were demolished so their materials could be repurposed for the larger structure. Excavation continued in phases through 1975, and a major restoration project ran from 1954 to 1959, during which the prefectural road running directly over the tomb was rerouted to allow proper investigation of the outer moat.

The name Ishibutai -- literally "stone stage" -- has been attached to this site since at least the Tokugawa period. A guide to Buddhist pilgrimage sites written by Kanenari Akatsuki in 1853 records it under this name, describing the exposed megaliths that looked like a platform built for performance. The name captures something essential about the tomb's character. Stripped of its mound, the Ishibutai does resemble a stage -- a platform of precisely fitted stone rising from a grassy amphitheater of rolling hills. Cherry trees now ring the site, and in spring the tomb is illuminated at night, the warm light turning cold granite into amber. The kofun was designated a National Historic Site in 1935 and elevated to Special Historic Site status in 1954. Today it anchors the Asuka Historical National Government Park, surrounded by the remnants of Japan's first permanent capital.

The village of Asuka served as the political heart of Japan from the late 6th through early 8th centuries, and the Ishibutai Kofun is just one node in a landscape dense with archaeological sites. Tanzan Shrine lies five kilometers to the east. The Takamatsuzuka Tomb, with its famous painted murals, sits nearby. Rice paddies and bamboo groves fill the spaces between, and the village itself remains remarkably rural -- a quality deliberately preserved through parkland designations. Visitors reach the site from Asuka Station on the Kintetsu Yoshino Line, and bicycle rentals near the station make it easy to explore the scattered ruins and monuments at a contemplative pace. Standing inside the burial chamber, surrounded by walls of granite fitted with a precision that modern builders respect, it is easy to forget that this was once hidden underground -- a private space for the dead, transformed by political revenge into one of Japan's most dramatic open-air monuments.