You just have to go to dmm.co.jp (the start page) click on japanese flag and then select japanese (日本語 - Look at the picture below) again at the top right of the page. After you select those two it will never bug you again, unless you reselect english.
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The only links that will not work without a proxy/japanese IP are the ones containing "/mono" in its URL address, which is the link to sell physical copies, you just have to replace in the URL "/mono/" for "/digital/videoa/". If you don't like it in japanese, just paste it on google translator and it will be the same, the english version was poorly translated anyway.