Director Quentin Tarantino, currently hosting a 'grindhouse' movie festival in Los Angeles, said he is developing 2 anime prequels to his 2-part feature "Kill Bill".He said one film will focus on "how 'Bill' became Bill" and the other will detail the backstory surrounding 'Beatrix Kiddo', codename 'Black Mamba', a member of the "Deadly Viper Assassination Squad".
It is not confirmed whether anime designer Kazuto Nakazawa who supervised "Chapter 3: The Origin of O-Ren" in "Kill Bill" (Vol 1) will handle the sequels. 
In the 15-minute segment, Beatrix, aka 'The Bride' (Uma Thurman) reveals that 'O-Ren Ishii' (Lucy Liu) rose to the top of the Japanese underworld, motivated by crimes against her family at the hands of 'Boss Matsumoto' and 'Pretty Riki'.
