(Referenced by 38; 133; 136)

This diagram shows a simplified version of the half-board seki, which could arise after Harry's variation for in our solution ( 135).
White's -group has no eyes, and shares common liberties (, five here) with Black's -group, which has one eye. Neither side is able to reduce the shared liberties to four. The number of these shared liberties depends on the size of the nakade () in the corner.

Normally, a hanezeki involves five chains (the Black and White groups in the bottom right, the nakade stones , and the hane group ). With the addition of the - and -chains, together with the single Black and White groups in seki, the circle is closed - hence the name of Circular Hanezeki.

This is the smallest, and simplest, Circular Hanezeki.

Larger, and more complex, ones can be created by having more pairs of groups in seki (including with large eyes), more nakade stones , larger eye sizes for and , and playing with the relative sizes of the various groups!

White must not capture Black's group.

After White captures Black's centre group and Black has recaptured, it takes Black two moves to fill White's eye (). Black must occupy a further three liberties (, one of which is an approach-move liberty) to capture White's marked group. Blacks group above has six liberties left, so White will be one step too late. If the hane group (the tail) is very large, then this could still benefit White.

Black must not capture White's three stones.

After Black captures White's three stones, and White plays inside, it takes White two moves to fill Black's eye (). She must occupy a further two liberties (, one of which is an approach-move liberty) to capture Black's marked group. White's group has five liberties left, so Black will be one step too late. Changing the sizes of groups can not benefit Black.

White must not occupy a shared liberty ().
Black plays at , captures three stones, and wins the semeai. Changing the sizes of groups can not benefit White.

Black must not occupy a shared liberty ().
White now plays at , captures the Black group, Black re-captures, ...

...and White wins the semeai. If White's group in the lower right corner is very large, this could still benefit Black.