Please find the best result for Black!
(japanese rules)
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[4]KM[0.00]
PW[Weiß]PB[Schwarz]AW[ba][bb][ac][cc][ad][cd]AB[ca][ab][cb][dc][dd]C[Black to play - what's the best he can do?]
;B[bc]CR[bc]
(;W[db]CR[db]
;B[aa]CR[aa]
(;W[bd]CR[bd]
(;B[bb]CR[bb]
;W[dc]CR[dc]C[Seki & Jigo (2 prisoners each)! RIGHT])
(;B[dc]CR[dc]
;W[bb]CR[bb]C[Uh oh... White wins!])
(;B[da]CR[da]
;W[bb]CR[bb]C[Uh oh... White wins!]))
(;W[bb]CR[bb]
;B[bd]CR[bd]
;W[ac]CR[ac]C[Nice try, but since there is no stone at D4, Black can capture at B4.]))
(;W[bd]CR[bd]
;B[bc]CR[bc]C[This was easy :)])
(;W[aa]CR[aa]
;B[ab]CR[ab]C[This was easy :)]))