So, checking my current source...
Spoiler for 61:
Looks like Kuesu really is gone
... however, it appears she has some last words for Yuuto, but who knows when those'll be translated. Along with talking to those guys in suits, it's possible that she may somehow return, though it's highly unlikely. Anyways, at the end of the chapter, Yuuto now has a glowy sword, which is Bad News for Tama and co... at least he didn't go emo, and I hope that those last words of Kuesu's were something positive, or that there might even be a possible return (but again, I'm not getting my hopes up on that one)
Looks like it's going to be a while before we find out anything specific, what with translations taking forever for this series