From: Patrick Davin <patrick <at> LYRA <dot> VEGA <dot> OR <dot> JP>
Date: 28 may 1999
Subject: Re: bogin defense

Hi Jackie and SHOGI-L,

Re: How to Defend in Shogi (http://www.vega.or.jp/~patrick/shogi/)

 l n - g k - s n l    s
 - r - - - - g b -
 p - p p p p p p p
 - - - - - - - - -
 - - P - - - - - -
 - s - - - - - R -
 P - B P P P P - P
 - - G - G - - - -
 L N - K - - S N L    PPP

>Now Oyama gives 33.  Bx8f, saying that 33.  Rx8f leads to an unfavorable
>semeai for Black after 34.  Rx8f  35.  Bx8f  36.  R*2f  37.  R*2b
>38.  G-7a.

>This last move is a finesse before playing 40.  Rx2i+.  Oyama does not
>mention how White would handle 39.  S*6b.  After the silver drop, I figure
>that Black has won; White's rook will not invade the Black camp (P*8g) and
>Black has such severe threats (P-7d).  So White should have played
>38.  Rx2i+.

>What am I overlooking?


Excellent question.  You appear to have overlooked nothing.

To summarize, from the diagram:
a) 33 Rx8f? Rx8f 35 Bx8f R*2f 37 R*8b:
    a1) 38... G-7a?
        a11) 39 R-8e+? Rx2i+ is clearly better for white
        a12) 39 S*6b! Gx6b 41 Rx8a+
            a121) 42... S*6a, or
            a122) 42... K-5b 43 P*2h S*7b are unclear at best
    a2) 38... Rx2i+ is still clearly better for white.  Black must
        either allow the S3i to be taken, or use the S in hand to
        defend it.  In the latter case, 40... G-7a will be good.
b) 33 Bx8f is still best.

As you point out, the attempted finesse 38... G-7a? is bad.  The author
apparently overlooked 39 S*6b!  On the other hand, Oyama's larger point
(that 33 Rx8f? leads to a bad semeai) is still correct.