Torazu sanmoku

Torazu sanmoku  

The traditional Japanese ruling, attributed to Honinbo Shuwa, was that this corner position was worth 3 points for Black at the end, without his having to capture the marked white stones. However...

After B capture  

... the Japanese ’89 rules make this seki if it is left on the board at the end of the game. Therefore Black should capture before the game ends (See diagram; may be delayed). The name is misleading under current Japanese rules and the same is true for another similar shape, Torazu Gomoku.

(continued)  

Black has gained 2 points in gote (White may play at a instead of and fight the ko to save 1 point).

Mathematical Go defends the 3-point ruling in terms of combinatorial game theory; see derivation for details. Note that this derivation is in terms of territory scoring, not stone scoring; see also the Discussion sub-page.

Chen Zuyuan claims that this rule is inconsistent with modern Japanese scoring, but is based upon stone scoring.

However, the traditional Japanese Go rules call it “three points without capturing”, which means there are 3 points for White. This obviously does not comply with present Japanese rules. But by the idea of “each side”, even if White moves first and there are “equal stones”, the result is still 3 points for White. This shows that the original Japanese rules are based on the concept of “each side”, and “three points without capturing” is its legacy.

The history of go rules, page 12

(Note: colors in the source are reversed, and by “each side” Chen means that each player plays the same number of moves/stones.)