When that voice resounds, it's Steph that Minako first glances at - maybe especially so since she can't spot whoever is talking, and she's trying to see from the other girl's reaction whether Steph has a single clue what's going on here or not.

Her reaction is hard to read though. Sure, Steph looks shocked, but who wouldn't be in this situation? Regardless of whether or not you'd actually recognize that voice.

So Minako also turns to look around them, trying to find the source. She contemplates things for a moment, but then decides to just speak up.

What's the use in keeping quiet if they've already been found anyway?

"What do you want?"

Nothing good, she bets, and so Minako frowns as she's voicing that question out loud.