Gai is Silvia's older brother and is well-known for stalking (yes, you heard it right). Silvia keeps a close watch on him and stops him whenever he most likely does so.

I'm looking for a medium-high pitched male voice for him. You can have a goofy nature if you like. I recommend listening to some other voice actors who has done Gai so that you can get a reference. Here is Gai played by Jaxoon.
https://youtu.be/gV9SdrdgB80?list=PL3xMwXz_E1kd-L3BndcQCYZytPZnD9z98&t=346