Welcome to the site and to UTAU in general.
Unfortunately, what you want to do is illegal unless you get explicit permission from the game developer (IDK if your aim is to make a vb based on the game character, but you need permission to avoid getting banhammered with copyright laws) and/or the voice actor to use their voice in the synth. Rule #1 of UTAU is that creation of a voice library must be consensual.