User blog comment:KodachiZero/Hatsune Miku Collaboration (Translated)/@comment-76.220.77.241-20141009002939/@comment-25251916-20141009040824

Under this banner http://www.crypton.co.jp/mikucolle_app/img/cp1_head.jpg, place your email and click the submit button to the right.

Luka is most likely going to be JP exclusive til further announcements. But she won't be obtainable until the app releases on the 28th, most likely.