It's poorly explained what this tag even is or what it looks like, leaving me to do a bunch of research on my own to try to understand it. It's the same dress worn by three different characters, but it's not exactly the same; there are slight differences in design that make it possible to distinguish which character it is. Irisviel's has a pencil skirt with gold-trimmed thighhighs, Illya's has a fleur-de-lis trimmed skirt and thighhighs, and Justeaze's is like Illya's but with a pelvic curtain. In the event of a cosplay you still have to (or should) tag which character is being cosplayed.