I've found their website and it's http://96tears.net/
Turns out that she's right and it technically is
?, at least sometimes. They go back and forth in how they write it, actually, as can be seen here: http://www.96tears.net/q.html
The Mysterians' website is pretty much useless, unfortunately, if information's what the girl is looking for. I knew what I posted off the top of my head, and that came from the book Bubblegum Music is the Naked Truth.
Here's Wikipedia's take on it all: http://en.wikipedia.org/wiki/%3F_%26_the_Mysterians