I don't know what your deviantart is so I'm not sure if you're one of the people in the link but worth a shot! https://www.deviantart.com/elle-rei/art/CE-Raito-and-Kei-435909305 Two of the comments refers to the characters as theirs, so one of them is probably the old owner of the one you're looking for 0: 

if it helps maybe you can look around the sources of the artists and maybe you can find out that way!

And you could also ask the previous owner