If White is strong on the outside, this invasion can be very severe.[2]
More about below [1]
Bill: I suppose that White played to avoid the L+2 group with descent. But then Black can seal White in with sente and attack White's wall on the right. (I suppose. How strong do we assume White to be?)
HolIgor: If white is strong outside this is not the first corner joseki. Black has a lot of options to avoid bad result. The joseki should not be applied automatically, that's all. Instead of black can choose a move that does not leave any weaknesses.
can be played at 9,
is not a must, one can allow white to connect and
if the surroundings in very hostile, black can choose to build eyes.[3]
Not good for White[4]
Invading at 3-3 right away gives White a cramped position. Black gets thickness and White only a small territory. That is, in the early stages of the game, where White can't afford to make the marked stone a heavy target. Instead of ...
Black can play here, completely shutting in White. If White lives with a, Black fixes up his shape with b. If White cuts at b, she risks being killed in the corner before her cut amounts to anything. Dieter
HolIgor: This is nice and well known but I am not sure that if white cuts at b and black makes hane to kill black would actually win the fight. The group in the corner has a lot of liberties and black is split into two groups. I cannot read it all. I have to try it for white. If I am killed then it is only one game lost, the experience is worth more. If I am not then it was a hamete.
Andre Engels: If black is not sure to win the fight, he should play on the outside first. At some point, he has a position where he can kill the corner, and white has to come back to resolve the corner, which means she loses an important tempo in the outside fight.
HolIgor: That's what the book says. Yet, the book does not show the cut. So, the problem is: let white cuts first, would it be that easy to capture the cutting stone? It is a difficult reading. At what moment black can either capture the cutting stone or kill the corner safely. If white has a stone on the side Yoshida does not recommend . Too dangerous. So, when safe and when dangerous? Difficult reading.
Bill: Well, I have a book that shows the cut, Suzuki and Kitani's Small Joseki Dictionary. Voila. and
are tesuji.
[1]
Why is necessary ? Can't Black kill the corner instead ? Well, ...
There is a ladder involved. If the ladder doesn't work ...
Both Black groups have four liberties. White's group as well. It looks difficult for White to reduce either of Black's groups' liberties. White a next is severest ?
[2]
Bill: looks bad, inviting damezumari.
[3]
Bill: If Black has to play this way, he is desperate. When White got strong on the outside (not shown in the diagram), why didn't Black close off the corner? Is it too early to resign?
[4]
Bill: You mean Black, don't you?
This is an amateur opinion page, not a reference.