1) Log into DMM.com
2) Switch the language of the site from English to Japanese (日本語) at the top of the site.
3) Open the Developer Bar (F12), put these lines into the Console and execute.

document.cookie = "ckcy=1;expires=Sun, 09 Feb 2019 09:00:09 GMT;domain=osapi.dmm.com;path=/";
document.cookie = "ckcy=1;expires=Sun, 09 Feb 2019 09:00:09 GMT;domain=203.104.209.7;path=/";
document.cookie = "ckcy=1;expires=Sun, 09 Feb 2019 09:00:09 GMT;domain=www.dmm.com;path=/netgame/";
document.cookie = "ckcy=1;expires=Sun, 09 Feb 2019 09:00:09 GMT;domain=log-netgame.dmm.com;path=/";