In Black Label or Black Novice get an x1000 (Gold)-multiplier.
Easy one !
You can do it in the first stage, collect enough green gems and switch to the Zesshikai mode (press once B) Shoot at enemies (in the purple bullet mode = Zesshikai ) and they produce some bullet flowers wait and switch back in normal mode (press once B again).
The Bulletflowers change her colour in blue, wait 1 -2 secounds and they transform in (Gold)-multiplier.