He had been shogun for eight months. Ashikaga Yoshikatsu was nine years old when he died on August 16, 1443 — thrown from a horse, according to most accounts, though some sources note dysentery as the cause, and others do not entirely exclude foul play. He had never governed. He had never been old enough to govern. The real power in the Muromachi Shogunate lived with the great shugo daimyo — the Hosokawa, the Yamana, the other great clans — who managed the boy's brief reign as regents while pursuing their own ambitions behind the ceremonial fiction of a child on the throne.

This was the second catastrophe to strike the Ashikaga bloodline in two years. Yoshikatsu's father, the sixth shogun Ashikaga Yoshinori, had been hacked to death at a dinner party in 1441 by the daimyo Akamatsu Mitsusuke — murdered while watching a performance, killed at a banquet that had been arranged specifically for the purpose of killing him. The assassination had succeeded partly because it was, among certain powerful men, a relief. Yoshinori had been strong-handed; the clans feared him. When he died at a feast, the daimyo who rushed in to 'suppress' the incident managed to ensure that the murderer was punished while the political conditions that motivated the murder remained intact.

Father murdered at a feast; son dead from a horse. The Ashikaga shogunal line seemed to carry a curse in the 1440s, and the clans circling the vacancy understood exactly what it meant. Yoshikatsu's successor was his younger brother, Ashikaga Yoshimasa. He was seven years old. Japan's government was now in the hands of a seven-year-old, following the death of a nine-year-old, following the assassination of their father.

Yoshimasa grew up. That, in a sense, was the problem. He became an extraordinarily refined aesthete — a patron of the arts who gave Japan the Higashiyama (東山) cultural tradition: ink painting, the tea ceremony, the nō theatre, the Silver Pavilion (銀閣寺, Ginkakuji). He was, by any cultural measure, one of the most significant figures in Japanese artistic history. He was also one of the least effective shoguns who ever held the title.

When his own succession crisis arrived in the 1460s — having promised the role to his brother, then suddenly producing an heir — he failed to manage it. The result was the Ōnin War (応仁の乱, Ōnin no Ran), which began in 1467 and burned for ten years. Kyoto was reduced to rubble. The Muromachi Shogunate never recovered real authority. The Sengoku era of continuous civil war followed directly from the power vacuum the Ashikaga left behind — that century of destruction that only ended when Oda Nobunaga marched into Kyoto in 1568.

All of that from a boy who fell off a horse in August 1443. Or got sick. Or, perhaps, was helped to fall. The bakufu (幕府) — the 'tent government' — kept standing after Yoshikatsu's death, but the main pole had quietly been pulled.