At the Kiyosu Council (清洲会議, Kiyosu Kaigi) in 1582, the great lords of the Oda alliance gathered to decide what would happen after Oda Nobunaga's assassination at Honnō-ji Temple (本能寺). Toyotomi Hideyoshi arrived with a plan already formed. He proposed that Nobunaga's infant grandson — the boy called 三法師 (Sanbōshi), barely two years old — be named the nominal Oda heir. The move was elegant: it honored the family line, bypassed Nobunaga's surviving adult sons who might actually use power, and let Hideyoshi position himself as the infant's protector. The boy who would grow up to be Oda Hidenobu (織田秀信) was a political instrument before he could form memories.

He spent his childhood as a symbol. As a young man he governed Gifu as a daimyo under Toyotomi patronage. When the Sekigahara Crisis came in 1600 and Japan divided between Tokugawa Ieyasu's Eastern coalition and Ishida Mitsunari's Western coalition, Hidenobu chose the West — drawn by Mitsunari's promise of expanded holdings in Mino Province. He was also, perhaps, loyal to the Toyotomi legacy that had made his position possible.

The Eastern Army moved faster than anyone expected.

On September 29, the preliminary battle at Komeno (小見野) ended with the defeat of 3,000 Western troops under Dodo Tsunaie (堂洞雲斎). By September 30, 1600, the Eastern forces — under Fukushima Masanori (福島正則), Ikeda Terumasa (池田輝政), and Ikeda Sen — had moved on Gifu Castle itself. The fortress sat on the summit of Mt. Kinka (金華山), a theoretically strong defensive position. But Gifu fell in under 24 hours from first contact. The speed was the message.

Hidenobu was 20 years old. Born March 9, 1580, he had lived his entire adult life in the shadow of a grandfather he had never known — a man whose name opened doors and also closed them, whose legacy defined what Hidenobu was supposed to be and made it impossible for him to be anything else. By the afternoon of September 30, he had been reduced to a few dozen men in the innermost keep.

He intended to die there. 切腹 (Seppuku) — ritual self-disembowelment — was the prescribed death for a lord who had lost his castle. It was a form of control over the one thing remaining. He prepared himself for it.

Then Ikeda Terumasa entered the ruins.

Terumasa had been one of the Eastern commanders who destroyed the castle. His forces had been part of the assault that swept through Gifu's outer defenses. And yet he came to the keep to argue against Hidenobu's death. The sources do not record what he said. They record only that he persuaded Hidenobu to accept the 開城 (kaijō) — the formal surrender, the opening of the castle gates to the enemy. Whether Terumasa was acting on Ieyasu's instructions (who may have wanted to demonstrate mercy to surviving Sengoku lords), out of personal regard for the young man, or for reasons the record doesn't preserve, is unknown.

Hidenobu descended the mountain.

At Jōsen Temple (常泉寺) in the town of Kamikanō at the base of Mt. Kinka, he stopped. He underwent 剃髪 (teihatsu) — the tonsure, the shaving of the head that marks the formal entry into Buddhist monastic life. The lord of Gifu Castle became a Buddhist monk that same afternoon, on the same day he had surrendered the castle.

The irony was visible to everyone who knew the history. Thirty years earlier, Oda Nobunaga had encircled Mount Hiei with 30,000 soldiers and burned Enryakuji to the ground — monks, women, children, buildings, and 800 years of accumulated Buddhist authority, reduced to ash in two days. Now Nobunaga's grandson was seeking sanctuary in the very institution his grandfather had tried to destroy. At Mount Kōya (高野山), the sacred Buddhist complex in Wakayama where Hidenobu was eventually sent under guard, the priests were notably unwelcoming. The irony, apparently, was not lost on them either.

Hidenobu lived out his remaining years at Mount Kōya and its surrounding area. He was expelled from the main complex at some point — exiled even from his exile — and retreated to the mountain's foothills. He died on May 8, 1605. He was 24 or 25 years old. The cause of death is disputed: contemporary sources mention illness; Kōya records suggest possible suicide.

The fall of Gifu sent ripples in two directions simultaneously. For Ishida Mitsunari, holding Ogaki Castle and receiving the news that same day: the psychological blow was severe. Gifu was not just any castle. It was the place Nobunaga had renamed — the old name was Inabayama (稲葉山) — the base from which he had launched his unification campaigns, the seat of the clan whose family member had just been unable to hold it for even a single day. If that castle, in those hands, fell in hours — what castle could hold?

Mitsunari's answer was to stop trying. He marched his entire Western Army out of Ogaki through rain and mud toward the plain of 関ヶ原 (Sekigahara), choosing open battle over a defensive war he no longer believed he could win. Sekigahara was twelve days away.

Gifu Castle was demolished by Tokugawa Ieyasu in 1601. He left nothing standing that could become a symbol of resistance. The Oda clan, as a territorial power in Japanese history, was finished. Its last lord had shaved his head at a temple and lived out five more years on a sacred mountain, unwelcome even there.