4-5 point 4-3 approach keima, contact at 6-3, vulgar cut
As a deviation from the joseki
White's cut with and has a vulgar feeling and requires a tesuji by Black.
invites , which is suicidal for White.
The only move with a snowball's chance in hell of getting White out of this mess is atari at . Black extends and White must connect at . Black now captures White with a loose ladder.
White's best defense is immediately to take a black liberty with .
Next, is an important kikashi. Black gives White sente. However, when the time is right, Black can come back and capture two white stones in sente by squeezing at a , making Black even thicker.
The result is not good for White, as Black gets good territory and influence and White's stones are overconcentrated.
at b, capturing two Black stones and saving all his stones, would be a small move, and Black has no need to answer: not worth losing sente.