On July 8, Shimazu Nariakira collapsed from heat exhaustion on the parade grounds at Tempozan while supervising military drills. He had been preparing to march 3,000 Satsuma soldiers to Edo — a show of political force timed to the mounting crisis over the shogunate's treaty negotiations with the West. Eight days later, on July 16, he died at Tsurumaru Castle in Kagoshima at the age of 49. This entry follows the traditional Japanese lunar calendar date; the Gregorian equivalent is August 24, 1858.

The oldest surviving photograph taken by a Japanese photographer is a portrait of Nariakira, produced on September 17, 1857. He had imported Japan's first daguerreotype camera in 1848 and spent nine years having retainers learn its chemistry before a successful portrait was achieved. His retainer Ichiki Shiro finally captured the image. After Nariakira's death, the photograph became an object of Shinto veneration, was eventually lost, and was rediscovered in a Kagoshima warehouse in 1975. It now sits in the Shoko Shuseikan museum — in the building Nariakira himself constructed.

That building was part of the 修斉館 (Shuseikan) industrial complex Nariakira built at Kagoshima: a reverberatory furnace for casting cannon, a glass factory, a spinning mill, a shipyard at nearby Sakurajima where one of Japan's first Western-style ships, the 伊呂波丸 (Iroha-maru), was constructed. He had done all of this not out of fascination with the West but out of strategic clarity: Japan would either modernize or be colonized, and Satsuma would lead the modernization.

Some contemporaries suspected poisoning, not heat stroke. The timing was notable: Ii Naosuke had just become the shogunate's Great Elder and was preparing both to sign the Harris Treaty without imperial approval and to launch the Ansei Purge against Nariakira's political allies. No evidence of poisoning has been confirmed, but the suspicion tells you something about how dangerous the moment was.

When Saigo Takamori learned of his lord's death, he resolved to die with him. He and a monk named Gesshō jumped from a boat into Kagoshima Bay. Gesshō drowned. Saigo was rescued, tried again, was exiled twice, and eventually returned to lead the very forces Nariakira had built — helping overthrow the shogunate in 1868. The Meiji Restoration was, in almost every structural sense, Nariakira's project completed by the men he had trained, using the weapons he had forged, on behalf of a vision he did not live to see realized.