What’s the crystal in her wrist

Wanna know 2

I read spoiler that everyone in this story has that stone, but it must be hidden because it's power source but also weakness (if the stone get destroyed, the person will die, something like that i guess), FL is already an adult and it's not normal that she can't hide her stone

Oh .o.

woah where'd you get the spoiler from? and is there a novel?

Interesting. Thank you!