Bang's nail is lynchpin right? Just modified or something like that
Also I'm convinced it's CP Ragna as well, at least after reading it again and coming across this line "Come to think of it, back when he met Celica for the first time, he felt familiar with the girl's gaze and her gentle expression. Perhaps, it was possible that he had met her somewhere in the future period. If so, it was a wonder."
Well one of them at least.