Sae is the older sister of Makoto. She's a no-nonsense, deadly serious prosecutor who undertakes an interrogation of Ren. Whilst she obviously doesn't agree with Ren in his morals initially, she clearly has sympathy for him due to his harsh mistreatment by the police prior. 

Her voice should be in a mid-low range. She is serious and straight to business yet not completely immune to frustrated outbursts. Although reasonably young (Mid 20's) her voice should hold a lot of maturity within it.

You can look at the game's dub actress, Elizabeth Maxwell, for reference.