As gote, how to defend against ☗６八飛 (sente's 2nd move)?
Book suggestions (I can read Japanese, though writing it is much more difficult) are much appreciated ;). Indeed there are many books about 四間飛車, but I'm only interested in those describing how to defend as gote against sente's early 四間飛車 (i.e. without closing the bishop's diagonal first).
Thanks in advance for your help! My level: 10級.
It is called 角交換四間飛車 (bishop exchange 四間飛車).
You can check some books by searching the word "角交換四間飛車", e.g. https://www.amazon.co.jp/dp/B00NHA4ID0 (I haven't read this).
Some web pages (http://blog.livedoor.jp/nifu_senkin/archives/46538612.html) describe 角交換四間飛車.
These books and docs might be hard for 10-kyu players but it will be interesting to read them.
try ☖8四歩 or ☖6二銀
i think ☖8四歩 better