Tales of Symphonia, being the first 3D game of the series, also was the very first game that introduced costumes. Because creating a different costume for a 3D model is easier than editing each and every sprite, I believe.The original Symphonia for the Gamecube was pretty generous, giving you 3 costumes for every character. A swimsuit set, a formal attire set and a pair of costumes not belonging to a certain theme, like Lloyd as a pirate, Regal as a cook or Raine as the Shrine Maiden. Kratos is an exception, because he doesn’t get a swimsuit and formal attire. But his Judgment costume makes up for it. Basically, 25 costumes to unlock. Remember those times where you can unlock costumes? Instead of them being paywalled by DLC? Good times!
The PS2 port added another set of costumes for every character, including Kratos. These are mostly (except Raine) tied to the Flanoir Event and are thus the most annoying one to get. Pick one character at Flanoir and you obtain 1-2 costumes. So you either finish the game multiple times and pick Kratos, Colette, Zelos, Genis and Regal at Flanoir to get them all or cheat as hard as possible and end up with dummy titles like Convict on Presea. For Raine, you must buy the most expensive item at the Casino.
The Chronicles port adds another pair of costumes. This time, each of the nine characters obtain Cameo costumes. If you have the save files of newer Tales game or finished this game, you immediatelly unlock them. Nice!
43 unlockable costumes in total.