Minami will have two voices. One where she is in her ghoul form, Jack, which will be menacing. In the scenes where she has her mask on you will have to add a very minor muffeled sound effect and make the voice genderless to hid the fact that Minami is Jack. When she is Minami, use a voice that has confidence and gentleness.

"Minami is an example of a Ghoul with a severely compartmentalized personality, neatly dividing her life between the human and ghoul worlds. While living as a human, she is a hard-working and cheerful girl that easily makes friends. However, as Lantern she is a cruel serial predatory noted for her extreme appetite and brutal killing methods. Minami has considerable admiration for the peaceful lives that humans led, and longs to experience that for herself through going to school. However, she also harbors intense feelings of jealousy towards humanity for their peaceful and easy lives. These feelings led her to carry out a twisted form of vigilantism, preying upon people that she believes do not deserve or appreciate the gift of living as humans. In this way, she is incredibly petty and cruel, viewing juvenile delinquents with the same disgust as hardened criminals because both disrupt the order of society. She claims to be doing human society a favor, through killing these "undeserving" elements."

( http://tokyoghoul.wikia.com/wiki/Uruka_Minami )