Problem 120 in Igo Hatsuyōron is not a simple classic hanezeki, as shown, and explained, before. This diagram is for reference, specifying the marks that will be used below.

There are 20 -stones, but 29 -stones ( included), so White does not profit from dissolving the hanezeki, here, as usual.

White's -stones (as a part of the classic -group) build a temporary seki with Black's -stones, which are not present in the classic hanezeki. The effect of this additional temporary seki will be explained later.