Kobayashi Fuseki

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Chinese: 小林流 (xiǎo lín liú)
Japanese: 小林流 (Kobayashi Ryū)
Korean: 고바야시 포석 (gobayashi poseok)

The Kobayashi Fuseki (Kobayashi Formation) is the pattern for Black shown below. It is named after Kobayashi Koichi who used it steadily at one point in his career. This fuseki has been actively played for some 20 years now ("now" referring to the year this article was first written, 2001). It is similar to the Small Chinese fuseki in that Black sets up a specific formation between the white corner in the lower left and Black's own open komoku stone in the lower right as part of a strategy for playing against a later white approach move there. It is an aggressive, fighting strategy.

The position along the bottom has a defect at e where White can invade rather easily. The other main variant in the Kobayashi is for Black to play 7 at f, attempting to eliminate the defect. However, this naturally gives White more options in the space around the lower right so opinions are divided on the placement of 7.

Black intends to use plays against an approach move in the lower right to naturally enclose the bottom side. At present the normal approach for White is the rather distant move at a. This is because closer moves tend to allow Black to play more aggressively:

a: This is the usual approach. Black prefers to shoulder-hit at c.
b: White strives to stay light; black usually responds at d and white tenuki.
c: Black responds with one-space high pincer or two-space high pincer.
d: Black wants to directly profit from attacking severely with a close pincer.

As with the mini-chinese, Black's ability to play this fuseki depends on White choosing not to answer Black 5 with a pincer. (See preferring to pincer.) Another way to counter it is to approach the right-hand corner. So if you don't like playing against the Kobayashi, you have only yourself to blame if it shows up in your games!

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AlphaGo Teaching Tool evaluation of the Kobayashi fuseki

Some fuseki moves can be evaluated by AlphaGo Teaching Tool.

First three are quite optimal. W #4 move has B winrate 46.5% but AGTT would prefer 3-4 move at D17 for 46.1% B winrate, thus about 0.4%-points better. As it is W turn, the smaller the *B winrate* the better the move for W.

The next Kobayashi fuseki moves #5 and #7 are not appreciated by AGTT. B approach at lower left yields 45.8% B winrate estimate, but two-space jump enclosure on right at P6 would be 46.1%, thus right side would be 0.3% better.

After W extending on left, the B move #7 at J4 leaves Kobayashi Fuseki diagram above evaluated at 41.9% winrate for B. Considering B starts the game with 47.1% it means according the AGTT evaluation for the fuseki B has lost 5.2% by move #7.

Instead of traditional #7 emphasizing bottom AGTT prefers right-side P6 for 45.5% or Q8 for 45.7%, both about 3.6-3.8% better than #7 of the fuseki.

Further for W #8, AGTT ranks the moves as:

c at 41.4% for B winrate (W likes as small winrate for B as possible)
d 42.1%
a 43.8%
b 44.0%

Further video analysis at [ext] https://www.youtube.com/watch?v=r_B2GQr6FJ8