There are several moves to secure life for black, but only one of them will win the game, too!
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[7]KM[0.50]TM[]
AW[da][fa][db][fb][dc][cd][dd][ed][fd][be][ce][bf][bg]AB[ca][ab][cb][gb][cc][ad][bd][de][ee][fe][af][cf][df]C[No komi, no prisoners - Black to play and win!]
(;B[ff]CR[ff]
;W[ge]CR[ge]
;B[gf]CR[gf]
;W[gd]CR[gd]
;B[ae]CR[ae]
;W[cg]CR[cg]
;B[dg]LB[fg:A]TR[ff]CR[dg]C[Black wins by one point! Thanks to the marked stone, the white endgame at the right was gote - if Black starts with A instead (also a commom idea), White would be able to play g4 in sente( see navigate solution for more details). RIGHT])
(;B[fg]CR[fg]
;W[gd]CR[gd]
(;B[ae]CR[ae]
;W[gf]CR[gf]
;B[ge]CR[ge]
;W[ff]CR[ff]
(;B[cg]CR[cg]
;W[ef]CR[ef]C[Black is dead....])
(;B[ef]CR[ef]
;W[cg]CR[cg]C[Black is dead....]))
(;B[ge]CR[ge]
;W[ae]CR[ae]
;B[cg]CR[cg]C[This is only a jigo!])
(;B[cg]CR[cg]
;W[ge]CR[ge]
;B[gf]CR[gf]
;W[ae]CR[ae]C[This is a desaster for black: white wins by one point!]))
(;B[eg]CR[eg]
;W[gd]CR[gd]
(;B[ae]CR[ae]
;W[gf]CR[gf]
;B[ge]CR[ge]
;W[ff]CR[ff]
;B[cg]CR[cg]
;W[ef]CR[ef]C[Black is dead....])
(;B[ge]CR[ge]
;W[cg]CR[cg]
;B[ff]CR[ff]
;W[ae]CR[ae]C[This is a two point loss for Black!]))
(;B[gd]CR[gd]
;W[cg]CR[cg]
(;B[dg]CR[dg]
;W[ge]CR[ge]
(;B[gf]CR[gf]
;W[fg]CR[fg]C[Black is dead])
(;B[ff]CR[ff]
;W[eg]CR[eg]
(;B[gf]CR[gf]
;W[fg]CR[fg]C[Black is dead])
(;B[fg]CR[fg]
;W[gf]CR[gf]C[Black is dead])))
(;B[ff]CR[ff]
;W[eg]CR[eg]
;B[dg]CR[dg]
;W[ge]CR[ge]
;B[gf]CR[gf]
;W[fg]CR[fg]C[Black is dead])
(;B[fg]CR[fg]
;W[gf]CR[gf]
(;B[ff]CR[ff]
;W[dg]CR[dg]
;B[eg]CR[eg]
;W[ge]CR[ge]C[Black is dead])
(;B[ge]CR[ge]
;W[ff]CR[ff]
;B[dg]CR[dg]
;W[ef]CR[ef]C[Black is dead]))
(;B[ge]CR[ge]
;W[dg]CR[dg]
;B[eg]CR[eg]
;W[ff]CR[ff]C[Black is dead]))
(;B[ge]CR[ge]
;W[ff]CR[ff]
;B[fg]CR[fg]
;W[eg]CR[eg]
;B[gf]CR[gf]
;W[gg]CR[gg]C[Black can't hope to win this ko])
(;B[cg]CR[cg]
;W[ff]CR[ff]
;B[gf]CR[gf]
;W[eg]CR[eg]
;B[fg]CR[fg]
;W[gg]CR[gg]C[Black can't hope to win this ko]))
