To get the Special CG Ending, finish the game with each character in Dreamcast 5.45 mode without continuing. When you do this with the last character, the Special CG Ending will play.

Note: You don't have to finish the game with Ajim for the Special CG Ending to play. Also, if you're having problems with the last boss, plug a 2nd controller and if you're dying at the last boss, press the Start button on Controller 2 to challenge yourself. This doesn't affect the code to get the Special CG ending.