: ( 509)
Black occupies a shared liberty in the hanezeki.

:
However, White takes a liberty of Black's group on the lower edge now, and not, as expected, of Black's top right group.

:
If Black captures on the left, White lives on the right. Black does not get White's partial group in the lower right corner, and White gets Black's partial group above, in the seki.

If Black played at , instead, White wins by giving atari at .