Kagura's got no reason to reincarnate, he had his magical "I'm okay with this!" turn around at the end which can only work if he's done with the reincarnating hullabaloo.
Zessica, Yunoha and Jin, and Shrade and Cayenne, are the only ones who'd have any even remotely arguable reasons to be reincarnated, but that just leaves Zessica alone unless ShuShu reincarnates to be with Mikono but ends up with Zessica (or we can go for a six man gambit with the listed characters).
You could probably pull some arbitrary reason out of someone's butt for why X character might reincarnate.
Amata reincarnates because his desire for a mom and dad!
Kagura reincarnates on his desire for SYLVIE! because why the hell not.
Mikono reincarnates out of a desire to accomplish something.
Operator-kun reincarnates out of a desire for more lines and scenes.
Etc...