From BFFs To Rivals

Friendship and rivalry look different, and clothes are one of the places the change shows first.

Friends borrow from each other. Rivals define themselves against each other. So the same two characters can be styled to look like they share a wardrobe, or styled so that every choice one makes is a rejection of the other, and the second version is much harder to do without it collapsing into two unrelated outfits.

The trick is that rivals still respond to each other. Keep one thing in common, even a colour, and the opposition stays visible instead of dissolving.