Étude Prologue: Yureugoku Kokoro no Katachi

While originally released in 1998 for Windows and Sega Saturn, this PlayStation 2 release came out 8 years later and contains many changes and updates. Basically, the game has been completely renewed, it contains new voice acting, new artwork, new music, and new gameplay system. The script has also been updated and extended resulting in much longer game story.

The PSP release which shares the same title as PS2 version, includes all the changes that were done in the PS2 version, and in addition it features the "Little Aid" sub-scenario which takes place a year before the main story. PSP version also uses widescreen aspect ratio which shows more of the picture than earlier versions.