Kingdom Hearts Birth by Sleep is a prequel to the series, released for the PlayStation Portable in Japan on January 9, 2010, and in North America on September 7, 2010 with additional content.
Kingdom Hearts Birth by Sleep Kingdom Hearts Birth by Sleep er en prequel til hele serien, udgivet til PSP i Japan den 9. januar 2010, og i Nordamerika den 7. september 2010 med ekstra indhold.