Spoiler:
But Marina
already knows him. It would be hilarious if she tries calling out to Setsuna in a crowded marketplace and Setsuna deadpans like, "Nope, sorry, you're mistaken, I believe you're referring to my twin brother/impostor/imaginary friend."
I mean, this kid can act, LOL.
Also, I LOL'd at the TV speech of Marina, if anyone cared to look at the lower right side of the TV screen.