Up to , Black lives. sure is a surprising move. It can be found when desperately looking for a way to make sente.
The result is a approach ko for White. ( is the approach move.) If Black omits in this diagram, White can simply fill a Black liberty -- no ko.
This is another variation where White cannot afford an attempt to kill Black, due to its sudden shortage of liberties, caused by the amazing 1-2 point throw-in.