Successfully complete Story mode.
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Complete the indicated task to unlock the corresponding character.
Successfully complete Story mode. Play Act 3, Stage 1 again with Amitie. In the intermission sequence, Amitie wants to join Draco Centauros' beauty contest and hears something in the bushes. Harpy and Witch from the original Puyo Puyo will appear from the bushes.
While on the title screen, Hold - (Minus) and press Up, Down, Right, Left, 1, 2. If done correctly, you will here a chime.