I'm in Japan. When I access http://www.kobobooks.com
it shows me Japanese titles only on the top page, as if I accessed http://rankuten.kobooks.com
. If I browse books through the left-hand menu there, it also shows Japanese titles only.
However, if I enter some English words on the search box, it shows me matching English titles, or for German words it shows German titles. So, I guess you can get listings of Japanese titles if you enter some Japanese words on the search box on http://rakuten.kobobooks.com