For the last forty years the Mainichi Shinbun (the newspaper sponsor of the Honinbo tournament) has hosted a game between the reigning professional Honinbo and the year's amateur Honinbo. The handicap in the game changes each year based on the previous year's results.
There are five incremental komi changes:
A loss by Black steps down this scale (komi decreases) in the next game while a win steps up this scale (komi increases). If Black wins while giving 5.0 points komi, the number of handicap stones decreases by one. If Black loses while receiving 5.0 points komi, the number of handicap stones increases by one. In both those cases, komi is reversed (treating each handicap stone as equivalent to 12.5 points komi). All steps from round to round increase or decrease.[1] In 2001 the amateur Honinbo lost on two stones receiving 2.5 points komi, so in 2002 Black placed two stones and received 5.0 points komi.
The 2002 amateur Honinbo was Samejima Ichiro who was appearing for the first time. The professional Honinbo was Kato Masao returning after 23 years.
Since 1995 the tournament has been played with free placement of the handicap stones. Black chose to place them on the 5-5 points in opposing corners. I am surprised that Black did not take the opportunity to play 2 at a.
White immediately settles the situation under the two 5-5 stones.
The game proceeded with heavy fighting and several large ko fights. Black won by resignation after 282 moves, preventing Black from being beaten down to three stones handicap (while giving 5.0 points komi). Next year the amateur Honinbo will play with two handicap stones and receive 2.5 points komi.
This comment is out of date. What happened in 2003, or this year for that matter?
The game is on the GoGod CD-ROM.
[1] Bob McGuigan: This komi system must be relatively recent because many changes in the past don't follow the rules given. For example, in 1964 the handicap didn't change after black won with 2 stones and no komi, and between 1971 and 1972 the handicap changed from 2 stones with no komi to 3.5 reverse komi.
Dave: Unfortunately my quite vague memory is that I took this material from an article in Go Weekly in 2002 so I can not check whether it said how far back the current system goes.
Bob: My impression is that the handicap was determined somewhat arbitrarily in the beginning. The lowest handicaps were given to such strong players as Kikuchi and even if he won, the next year the amateur might have a higher handicap. I also wonder whether the pros didn't take things as seriously in the beginning as they do now. This could be a partial explanation for the much higher handicaps in recent years.