From Tengen to the Stars: The Father of Modern Japanese Calendar
The Boy with the Brightest Mind
In the prestigious Yasui Go house, one name began to stand out—not for pedigree, but for brilliance.
His name was Shibukawa Shunkai (澀川春海).
He was a prodigy. A student of Go, yes—but also of the stars. Shunkai studied astronomy with a passion that rivaled his commitment to the board. He believed the Go board was not just a battleground of minds, but a mirror of the cosmos itself.
In his mind, the center point of the board, Tengen, was the sun. A gravitational anchor. A spiritual core. From this belief, he formed a theory that would one day put him in front of the Emperor.
And bring him to his knees.
The Theory of Tengen
According to Shunkai, if the first black stone was placed on tengen, the entire board could harmonize around it. Eight directions of power. Eight arms of influence. A single point to rule the board.
He believed in it deeply.
And he wasn’t alone. A few of his peers began to follow the same line of thought. In some circles, his theory was whispered as revolutionary.
It wasn’t just Go. It was celestial mechanics.
But the Go world doesn’t run on ideas alone—it runs on games. And games must be won.
The Most Important Match of His Life
In 1671, the Go world was ablaze with tension.
The Honinbo and Yasui houses were deep into a political and personal war. Honinbo Doetsu and Yasui Sanchi were locked in a twenty-game blood feud. Every victory shifted the court's favor. Every loss stained reputations.
That year, the pairings for the Castle Games (Oshirogo) were announced.
Shibukawa Shunkai, still young but already ambitious, was selected to play as Black. His opponent was the most feared player of his generation:
Honinbo Dosaku—the same prodigy who had helped dismantle the Yasui political stronghold.
This was Shunkai’s stage. His moment.
And he made a vow before the game:
“If I play Tengen and lose, I will never play it again.”
The palace held its breath.
One Move, One Collapse
He placed his first stone on Tengen.
The game that followed was fierce and fast. Dosaku played with his usual brilliance—flowing, sharp, suffocating.
Shunkai held his own, but the center point—the very soul of his strategy—never gained traction.
By the end, he lost by nine points.
Shunkai was devastated. Not just because he had lost, but because the universe he believed in had crumbled.
Silence and Shame
He withdrew from the public eye for three months. Locked himself away. Refused visitors. Refused matches.
True to his word, he never played tengen again—not at the start of the game, not even as a tactical move later.
He had built a cosmology at the center. And it had betrayed him.
But Shunkai was no ordinary man. He wasn’t destined to vanish in defeat.
A Different Destiny
Japan’s calendar at the time was based on traditional Chinese methods—systems that worked well in China’s geography, but not in Japan. As a result, Japan had experienced two failed solar eclipse predictions, shaking public trust.
Shunkai—who had once seen the cosmos in a Go board—now turned fully to the skies.
And in those stars, he found his second life.
The Man Who Changed Japan’s Time
In 1684, Shunkai was appointed the official astronomer of the Tokugawa shogunate.
He went on to develop the Jokyo calendar, publish works like Tenmon Seisho and Nihon Chōreki, and correct centuries of astronomical misalignment.
He became the father of modern Japanese calendrical science—a man whose defeat on the Go board freed him to realign an entire nation’s understanding of time and the heavens.
The True Victory
Looking back, Shunkai’s loss to Dosaku was a turning point not just for Go but for Japan’s scientific awakening.
He believed in the power of the tengen—not because it was strategically perfect, but because it gave him a lens to understand the world.
When the board failed him, he lifted his eyes higher.
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Copyright Notice
This English adaptation is based on Japanese Go Stories (《日本围棋故事》, 2016) by Xue Zhicheng (薛至诚).
For non-commercial use only: Shared for educational purposes under fair use.
Rights retained: All copyrights belong to the original author and cited sources.
Modifications: Minor narrative adjustments were made for readability; all historical content remains accurate.
No affiliation or endorsement: This work is independent and unaffiliated with the original author or publishers.
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References
Adapted from:
Xue Zhicheng (薛至诚), Japanese Go Stories (《日本围棋故事》), 2016.
Cited in original work:
Watanabe Hideo (渡辺英夫), Shin Zaigin Dansō (《新坐隱談叢》)
Watanabe Yoshimichi (渡部義通), Kodai Igo no Sekai (《古代囲碁の世界》)
Lin Yu (林裕), Weiqi Encyclopedia (《围棋百科辞典》)
