Link between tags already exists, but in wrong direction. Seeing as danbooru goes by original name being main, "black_magician_girl" should be main in this pair as seen from kana in card name: http://yugioh.wikia.com/wiki/Black_Magician_Girl.
Some other YGO card-based characters need similar treatment. Should I post them here or in different thread?
Updated by Hillside Moose