In this 9x9 game, Black, playing with a three stone handicap, could have won on territory quite easily, but he surprised white by killing the white group on the left. How did he do this?
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[9]KM[0.00]TM[]
PW[Weiß]PB[Schwarz]AW[ab][bb][bc][ad][cd][ce][de][ee][cf][ff][hf][fg][eh]AB[ba][cb][db][cc][ec][gc][dd][ed][fe][ge][df][ef][bg][cg][dg][dh]C[Black to move and kill the white stones on the left]PL[B]
(;B[af]CR[af]
(;W[ae]CR[ae]
;B[be]CR[be]C[Now white can't play b4, so he is dead RIGHT CHOICE])
(;W[be]CR[be]
;B[ae]CR[ae]C[b6 is a false eye, so white is dead RIGHT CHOICE]))
(;B[bf]CR[bf]
;W[be]CR[be]
;B[af]CR[af]
;W[ae]CR[ae])
(;B[be]CR[be]
;W[bf]CR[bf]
;B[af]CR[af]
;W[bd]CR[bd])
(;B[ae]CR[ae]
;W[af]CR[af]
;B[bf]CR[bf]
;W[be]CR[be]))