Aura- Crystal

Aura code- Boo Velka Receptor Arba

Also known as Buu in the manga. Boo is a demented rabbit with very strong Aura powers who attaches himself to Ai as Ai's "Master", believing Ai to be one of the next great "Aura Masters", and it is through "Master Boo's" training and help that Ai first starts to discover how to use some of his own Aura power, and learn it rather quickly and expertly. Boo's Aura specialty are Crystals.