Board Thread:Questions and Answers/@comment-32757117-20170803014555/@comment-24830484-20170805221249

Quirks are basically paranormal mutations present since birth. People start to develop the paranormal aspect of them around the age of 4, but physical manifestations appear since birth. Like the glowing baby. So I would assume in Tokoyami and Ashido's case they were born looking different and their powers developed later.