I found this tesuji during one of my blitz games. 4kyu vs 5kyu. I was the 5kyu.
Please feel free to add variations or correct me if I have analyzed this problem wrong.
(;AB[bc]AW[ad]AW[bd]AB[cd]AB[dd]AB[de]AB[df]AW[cf]AW[ce]AW[cg]AW[dg]AW[ch]AB[dh]AB[eg]AB[fg]AB[ff]AB[di]AB[bj]AB[cj]AB[aj]AW[ai]AW[bi]AB[ci]AW[eh]AW[fi]AW[ck]AB[cl]AW[dl]AW[em]AW[fl]AW[dn]AW[cn]AW[an]AB[gl]AB[hk]AB[il]AB[hm]AW[gm]AW[gn]AB[hn]AW[fc]AB[jc]AB[nc]AB[pd]C[Black to save his stones and capture all of white's group.]AW[ag]AW[ef]AW[bn]AP[goproblems];B[bh]
(;W[ah];B[af];W[bg];B[be]
(;W[bk]
(;B[ej];W[fj];B[ac];W[ak];B[ae];W[dj];B[dk];W[ei])
(;B[fj];W[gj]
(;B[fh];W[ei];B[gi];W[ej];B[ek])
(;B[ei];W[fh]
(;B[fk]
(;W[ej]
(;B[ek]
(;W[dk]
(;B[dj];W[ak];B[ej];W[gk])
(;B[gi];W[gh];B[dj];W[ak];B[ej]TR[gi]MA[gk]C[Right. With the triangle stone white can't push.RIGHT]))
(;W[gi]))
(;B[gi];W[gh];B[ek];W[dk];B[dj];W[ak];B[ej]MA[gk]TR[gi]C[Right. With the triangle stone white can't push.RIGHT]))
(;W[gk]C[White mistake, white has a better resistance.];B[gi]
(;W[gh];B[hj]C[RIGHT])
(;W[hj];B[gh]C[RIGHT])))
(;B[gi];W[gh];B[fk];W[ej];B[ek];W[dk];B[dj];W[ak];B[ej]TR[gi]MA[gk]C[Right. With the triangle stone white can't push.RIGHT]))
(;B[gi]
(;W[ej];B[ei]C[RIGHT])
(;W[gk];B[ei]C[RIGHT])
(;W[fk];B[fh]C[RIGHT])
(;W[gh];B[fh]C[RIGHT])))
(;B[ac];W[ei]
(;B[ae];W[dj]C[Behind in the semai. Black can do better.])
(;B[ej];W[dj];B[dk];W[ak];B[dj];W[fj]))
(;B[ei];W[fh];B[fj];W[gj]
(;B[fk];W[ej]
(;B[ek];W[dk]
(;B[dj];W[ak]
(;B[gk])
(;B[ej];W[gk]))
(;B[gi];W[gh];B[dj];W[ak];B[ej]TR[gi]MA[gk]C[Right, with the triangle stone white can't push.RIGHT]))
(;B[gi];W[gh];B[ek];W[dk];B[dj];W[ak];B[ej]TR[gi]MA[gk]C[Right, with the triangle stone white can't pushRIGHT]))
(;B[gi];W[gh];B[fk];W[ej];B[ek];W[dk];B[dj];W[ak];B[ej]TR[gi]MA[gk]C[Right, with the triangle stone white can't pushRIGHT])))
(;W[ei];B[dk];W[bl];B[bk]
(;W[cm]C[A small white mistake. Black can play F9 to avoid the semedori with a ko, assuming he has ko threats.RIGHT]TR[fk]TR[ac]
(;B[ac];W[ck];B[ae];W[ek];B[bf];W[dj];B[bh]C[Black eeks out a winRIGHT])
(;B[fk];W[ek];B[ej];W[fj];B[el]C[RIGHT]))
(;W[ek]C[Black has to play out the semedori now. Best result for whiteRIGHT];B[ac];W[cm];B[ae];W[ck];B[bf];W[dj];B[bh]C[RIGHT]))
(;W[dj]
(;B[bk])
(;B[ei];W[fh];B[fj];W[gj]
(;B[gi];W[gh]
(;B[ej]
(;W[fk];B[dk]C[RIGHT])
(;W[dk];B[fk]C[Withe G11 there, white can't push.RIGHT]))
(;B[fk];W[ej];B[bk];W[dk];B[al];W[bl];B[bm];W[cm];B[ac];W[am];B[ae];W[bl]C[One behind. You must connect out.]))
(;B[ej]
(;W[fk];B[dk]C[RIGHT])
(;W[dk]
(;B[gi];W[gh];B[fk]C[Right. With the triangle stone there white can't push.RIGHT]TR[gi])
(;B[fk];W[gk];B[gi]C[RIGHT]))))
(;B[ej];W[ek];B[fj];W[gi];B[ei];W[fh];B[gj]C[RIGHT])))
(;W[bf]C[White thinks he has a ko. Prove him wrong.];B[ah];W[ae];B[bg];W[bi]
(;B[af]C[No ko, black can do better]MA[ai])
(;B[ai]C[From here white has few options, all bad. Feel free to add variations and comments about the play after or before this point.RIGHT]
(;W[cc];B[cb];W[dc];B[ec]C[This doesn't get white out of it])
(;W[bk]
(;B[ac];W[ak];B[af]C[3 step ko in black's favor, black takes first?? go black!])
(;B[fj];W[gj];B[ei];W[fh]
(;B[gi];W[gh];B[fk];W[ej];B[ek];W[dk];B[dj]C[No ko.RIGHT])
(;B[fk];W[ej]
(;B[gi];W[gh];B[ek]C[RIGHT];W[dk];B[dj]C[No ko.RIGHT])
(;B[ek]C[RIGHT]
(;W[dj])
(;W[dk];B[dj];W[gk];B[gi]C[RIGHT])))))
(;W[ei];B[bk];W[dk];B[al]C[Avoid the ko and the semidoriRIGHT])))
(;W[bg];B[ah]C[Please add variations hereRIGHT]))