I doubt he is loosing any sales because of this. You can't even buy the book outside of japan. I would 100% buy the book if I was able, but at the moment the best that is available is this crappy google translate version.
Hi! I know this is completely unrelated, but hackernews has no PM functions, so I'm posting this here. Schoen, you posted a comment on here a couple of years ago looking for an English translation to a book on obfuscated programming. I could not find much info online about getting an English copy and I also really wanted to read it, so I threw a copy into google translate, and its surprisingly readable. Since you are one of the only people I could find online also looking for an English copy, I just wanted to make you aware of its existence. If you don't care about this at all, sorry for bothering you. If you do care, here is a link: https://obfuscationandesotaric.neocities.org/
Have a great day!