The following story first saw the light of day in an old Japanese book called "Kokon Chobun-shu" (Collection of Remarkable Stories of Past and Present). Its currency among go players, however, is really due to Hayashi Genbi who included it in his ever fascinating "Rankado Kiwa" (Hayashi Genbi's Go Stories) of 1849.
You will find it easier to understand if you first study the position below, which features a double-ko seki and a separate group with one eye and half-point ko.
On the 29th day of the 12th month in the 5th year of the era Kencho [1253], a monk called Gyobubo visited another monk called Hoshinbo. They played "two-person go" and in the course of the game Hoshinbo formed a one-eyed group with a half-point ko attached. A double ko had evidently already been formed and obviously was not in itself something that troubled them. But Hoshinbo now claimed that his little one-eyed group could not be captured. Gyobubo countered that it had just one eye, and the ko was not enough for it to make another eye. There was no other means of escape, such as nearby capturing race.
Hoshinbo accepted that that was the normal case, but pointed to the double ko elsewhere on the board and argued that he could use this for unlimited ko threats, so his opponent would never be in a position to win the ko in the small one-eyed group (and thus could never capture it by filling in all its liberties). Gyobubo, however, could not see why one apparently independent group should govern the life or death of another one. They could not reach agreement and resorted to higher authority.
We do not know the position they argued about. Indeed, if we had to rely only on the original text it would be difficult even to reconstruct an analogue of it. But perhaps the details passed down through oral tradition and players in later ages knew what was meant. We now assume it was something like the position above.
The two monks turned first to a player known as Hogen Shunkai of Bitchu (now Okayama prefecture) who had a reputation as an expert. Shunkai took the whole-board view of Hoshinbo and passed down a ruling summed up as "ryo:ko: ni kasho:" with ryo:ko: (double ko) in characters and kasho in kana. We therefore have to guess at the meaning of kasho: but it seems accepted it was [double ko and] "provisional life."
Next they consulted a monk called Nyobutsu. From his name - like a Buddha - he was obviously someone who had a reputation beyond that of a mere go player, but his ruling was the same as Shunkai's: the group may just have one eye, but because of the presence of the double ko it is not dead."
However, the matter arose again in Bunsei 4 (1821) when it was brought to light by the Confucian scholar Ota Hachiro (also called Ota Bungaku) from Fukuyama. He deduced what the position was and passed a diagram to the heads of the hereditary go families for their opinions. A conference was held, chaired by Honinbo Genjo. His fellow panellists were his great friend and rival, Yasui Chitoku, Inoue Insa, Hayashi Genbi and Hattori Inshuku.
The problem was already 500 years old by then but that did not stop them overturning the traditional judgement of Nyobutsu. They took the view that the local-board positions were paramount. Groups had to live independently.
Ota Bungaku apparently was not satisfied with the ruling (or perhaps the reasoning) and so the issue remained live. Eventually it resurfaced in Meiji times when, according to the great compendium of go history, Zain Danso, it was put to "the leading authorities" of the day. We do not know whether this means Honinbo Shuho or Honinbo Shuei, but it must have been one or the other. At any rate the ruling was changed back to the original one by Nyobutsu and remained in force, as a tradition, until the Nihon Ki-in first formalised its rules in October 1949 and switched back yet again to the Genjo ruling.
