Cast the Sword Brothers spell, Press the Directional Pad D, DF, F, UF, U(hold UP 3 seconds) D + Attack. As the sword starts to spin, walk towards the librarian and enter his menu. Sell all but 1 of any gem. Press start to enter into Alucard's menu while still in the librarian menu. Equip Alucard with the last gem. Sell it causing your gem count to glitch. This is similar to certain Pokemon glitches.