Unfortunately, Japanese summers are very humid and soon your books will smell "kabi". There is only one solution: digitize them. It only takes a cutter, a scanner, lots of time and coffee. Or you check the internet, there are companies doing this for you - check with the keyword "本pdf化". A mess (and you don't even see the backside). Nicely ordered according to the book sizes - speeds up the setting of books in the cutter. A paper cutter, I used this one time and experience a scanner, this one is from Brother and coffee and after some time it looks like this No more kabi smell.