Pro-Am Honinbo Match

(プロアマ本因坊対抗戦) Each year since 1963, 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 first match in 1963 was played by Harada Minoru (a 5d amateur at the time) and Sakata Eio 9p. The handicap was 2 stones, no komi. The handicap changed erratically during the first 26 terms^[1] and the amateurs went 9 in 26. After that, starting in 1989, the handicap has been adjusted regularly and has varied from a minimum of the amateur just taking black with -5 komi to an enormous 3 stones and -2.5 komi that Harada (again, 34 years later!?) received 1997 against Cho Chikun (and lost).

However, Iwai Ryuichi may have started a trend to lower that handicap, winning against O Meien in 2000 with a mere 2 stones and -5 komi.

Amateurs would of course love to be able to get the handicap back down to just playing black with komi.

Handicap System

The handicap in the game changes each year based on the previous year's results.

There are five incremental komi changes:

• Black gives 5.0 points komi (jigo is possible)
• Black gives 2.5 points komi
• No komi (jigo is possible)
• Black receives 2.5 points komi
• Black receives 5.0 points komi (jigo is possible)

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.

In 2003, a similar new system where one "step" is 3 points was introduced.

Free Handicap

Since 1995, free handicap have been used in the event. Cho Chikun, who played many games as the pro Honinbo, suggested using the free handicap when he beat down amateurs to 3 stones.

Results since 1989

[2] Muraoka was the runner up in the tournament. The tournament winner Sakai Hideyuki, later pro and Gosei, declined to play receiving a handicap.
[3] See Amateur Honinbo vs Pro Honinbo 2002 for the opening of the game.
[4] Tsuneishi Takashi didn't play because he had turned pro soon after winning the tournament.
[5] Played in Feb 2023.

Japanese Wikipedia has a complete list (in Japanese of course) on its Amateur Honinbo page.

[1] Bob McGuigan: The handicap system seems to have been instituted for the 1989 term. According to the Japanese go yearbook the handicap varied quite a bit in the early years and there does not appear to have been a formula. In 1965 Black received 5 points komi (Kikuchi beat Sakata); in 1971 Miura lost to Ishida with two stones but in 1972 Kikuchi lost to Ishida with only 3.5 reverse komi. It moved around thereafter reaching a low of 3.5 reverse komi and occasionally going up to 2 stones or a little more. Pre-1989 highlights for the amateurs include Kikuchi's defeat of Sakata with 5 point reverse komi, his defeat of Rin Kaiho with 4.5 reverse komi and Nakazono defeating Takemiya with 5 points reverse komi in 1985 and 1987. The amateurs had a 12 game losing streak from 1970 through 1981.