It's... all of the series protagonists?
Is Yusei gonna show up and turn out to be the most bad-ass embodiment of hope and caring ever envisioned?
Or am I missing something here...
As for it being a card, I actually have an idea on that front, what about the maiden with eyes of blue? After all BEWD is probably one of the most iconic light monsters in the game and while his raw power isn't entirely apropos for a spirit of hope and love or what have you, the maiden does sort of fit while still having that emblematic sort of connection?
(Also I've been watching more Yugioh related stuff and I really like the maiden, her story is a sad story, and if you don't use her, I might make an expy of her as another main character later on.)
Also also I am so bad at all of the genders in 5Ds, first the gremlin, now Rally is apparently a boy too? I would not have guessed until episode 28 where they mention 'him' a whole bunch.