(;
AB[rp][rq][qq][qr][nr][or][pr][os]
AW[qo][qp][ro][lq][nq][oq][pq][kr][mr][rr][sr][ns][qs]
C[Black plays.]
(;
B[ms]
C[Creating an extra liberty here doesn't work.];
W[rs]
C[White creates a "one eye vs. no eye" situation.  The corner is not a seki.  Black is dead.];
B[so]
C[For example ...];
W[sn];B[sp];W[rn]
C[If Black fills a liberty on the inside, White will create a dead 5 shape.

So, if necessary, White can fill the outside liberties and then atari Black from the inside.]
)
    (;
    B[sp]
    C[Descending here fails for the same reason as the previous variation.];
    W[rs]
    )
    (;
    B[rs]
    C[This throw-in looks promising, but ...];
    W[sp]
    C[... because Black has a liberty shortage, White can connect to the 2 stones.];
    B[ms];W[sq]
    )
    (;
    B[so]
    C[The only move.];
    W[rm]
    C[To keep Black from escaping.];
    B[rs]
    C[Now Black can throw in.];
    W[ss];B[sp]
    C[The corner is a seki, because without an eye, White cannot approach from the inside.]
    )
)

