User blog comment:KodachiZero/Hatsune Miku Collaboration (Translated)/@comment-76.220.77.241-20141009002939/@comment-25251916-20141010004542

Check your email and it will be in japanese kanji. It just basically means your pre-registration is complete. Also note, this method to gain Luka is only available for Japan at the moment. Only go through this pre-registration if you have a JPBF account.

For Global, there is the New York Comic Con event. They are handing out flyers with the serial codes for Luka.