I'm trying out the 50/50 chance for the first time, I have enough for 80 rolls and change. If I lose and the banner expires and switches to the next character, will the next S-rank I get in that banner be a guarantee for that new character or does it reset back to the permanent pool?

Usually I save up enough to get all the way to 160 rolls for a character. I don't particularly want this one, but at the same time there's literally no one else besides her that I'm even remotely interested in based on the 2.0 trailer.