Sou is a complex character with multiple personalities. To a majority of the group, Sou behaves as an incredibly helpful, generous and knowledgeable figure. Similar to the main cast, Sou plays a heavy hand in contributing to the group's advancement. Although, when speaking to Sara alone, Sou reveals a more threatening side as he stresses his disdain and distrust for her. He frequently uses his own intelligence in manipulation to get other participants to do his bidding as well, and often will derail discussions for seemingly his own amusement.    

Sou's voice should show a very high variety of emotions because of how he acts. I imagine the range for him is medium to medium-high.