Board Thread:General Discussion/@comment-25266931-20151115205337/@comment-25209034-20160311200140

ChishioKunrin wrote: Vongola Mist Guardian wrote: Sage and Fox's designs interest me the most, with Fox they're in a world with personal force fields that protect them from injuries but he's covered in scars that his aura should have protected him from so there should definitely be an interesting story behind that. He could've gotten those scars before he unlocked his Aura.

Apparently, you have to unlock your Aura in order for it to actually protect you. They could also be birth scars.