(;AB[ca][bb][cc][bc][bd][db][ea][df][ef][fg][fh][dh][di][ej][dk][cj][bj][aj][ai][el][dm][fm][em][dn][bn][am][an][ao][br][cr][cq][cs][eo][ep][eq][er][fr][gr][hr][is][gn][hl][hm][hk][gj][gi][gf][ge][gd][gc][hf][if][jg][jh][ji][kh][kj][lk][ll][kl][lm][kn][jn][in][kp][lp][mo][nn][nm][np][nq][nr][mr][os][ps][qs][sq][sp][rp][rn][qn][qo][po][oo][qm][ql][pk][ok][oj][ni][mh][mg][mf][me][nd][nc][oc][oe][pb][qb][pa][oa][rc][ka][kc][kf][ke][la][ja][kb][jc][kd][ib]AW[ad][be][cd][dc][de][ee][fe][ff][fd][fc][fb][eb][gb][hb][ic][hd][id][je][jf][cf][cg][ch][ci][bi][ah][gg][hg][ig][hi][hj][ij][ik][jk][kk][jm][im][km][al][bl][cl][dl][cm][cn][co][do][bo][bq][bp][aq][ar][ds][dr][es][gs][hs][ir][iq][hq][gp][fp][en][fn][fo][ho][hn][jo][ko][lo][ln][mn][or][oq][op][qq][qp][rq][qr][sr][rs][sn][ro][rm][rl][rj][qk][pj][pi][oh][nh][of][pf][qg][pd][pc][qc][rd][rb][ra][ob][nb][ma][lb][lc][mc][ld][le][lf][lg][kg]C[Black plays.

Source:
     "Upsetting Moves", Sonoda Yuichi 8P
     Go World #10, p. 49]SZ[19]

(;B[lh]C[This move looks huge, but is nearly worthless, as you'll see in the next variation!

Black's intention is to capture White's group above.];W[qa]C[For example, White can capture the 4 stones to the left, but ...];B[md]C[... Black catches White in a liberty shortage.  Black captures the 8 stones and saves the 10 stones at the top middle.])
(;W[qa]C[The reason that the previous sequence is nearly worthless for Black is that even if White plays here first, Black still captures White's stones!];B[lh];W[na];B[md];W[mb]C[And if White tries to save the 8 stones, the situation becomes even worse for White.];B[pb]C[Black uses an under-the-stones tesuji to capture even more stones.])
(;B[hh]TR[gg][hg][ig]C[Black can also capture the marked stones to save the 6 stones above those marked stones, which is worth 20 points.

But Black has a much bigger move.])
(;B[fs]C[Capturing here looks perfect.  Black seems to make 2 eyes with the bottom left group.  And because White's bottom left group has only 1 big eye, White seems to be in serious trouble.

But ...];W[hs]C[... White has this throw-in surprise.];B[dq];W[ds];B[js];W[kr]C[White closes off the escape.  Now both sides are in a winner-take-all liberty race.

But the go proverb says, "A big eye beats a small one."  White's big eye on the left side gives White the advantage in the semeai.

Try to count the liberties for each side before playing through the following sequence.];B[ak];W[jr];B[bk];W[ks];B[ck];W[is]
;B[bm];W[as];B[cp];W[gq];B[dp];W[fq];B[bs];W[ap]C[Black obviously has no chance to win the semeai.])
(;B[js]C[The game winning move.

Black fixes the problem in the previous variation, by threatening to connect out to the right.];W[kr]C[White can still block the escape, but ...];B[dq]C[... next Black threatens to simultaneously capture 3 stones and 2 stones, after which Black makes 2 eyes.

The difference between White or Black winning the semeai in this area is over 80 points!];W[hh]C[Now White has nothing better than to save the center stones.];B[lh];W[qa]C[The dust has settled with Black winning by about 16 points on the board.]))