Director Hajime Tabata popped up on Twitter to tell fans there won’t be any downloadable content for The 3rd Birthday. For this game, the development team tried working with the Square Enix members group instead.
You can collect stamps with a Square Enix members account, which unlock Over Energy (ability) chips and the Lightning costume for Aya. Stamps are earned by adding Square Enix members friends, writing a The 3rd Birthday journal, and giving your Square Enix members avatar a prop from The 3rd Birthday.
Tabata explains Square Enix was investigating a collaboration between members and a game. The 3rd Birthday is the first title to test this out and in the future other games may take advantage of this service.
While a Square Enix Members service is online in North America, it isn’t clear if the Western version will use the same unlocking system.