How does black kill white in this Tsumego?
Seems Black has to take the 1-2 vital point to avoid White making 2 eyes. If White begin to deprive Black's liberty from outside, then Black get connected by taking on 1-3 and White deprives outside again. After that, both Black and White have same 3 liberties, but 2 of them are in common used. This becomes seki and it should be the best result for White.