Black starts at the 1-2 point. Usually, White keeps this shape to one eye, but here there is aji in . The key move is . After , Black can either capture four stones in shortage of liberties at a, or make two eyes at b.
Because of the presence of , doesn't work. and are miai, and so are a and b.
If here, White destroys his eye with .
Now and are miai to take the eye away.