Haha, no, you shouldn't have to do that. That's why I got these.

[ He points to his back where an extra pair of shorts are. ]

I'll change into those and give you my jersey. It should be fine.

[ He has little shame in being shirtless, and he wouldn't make a cute girl suffer any kind of embarrassment or indignity like that. He may be carefree and irresponsible, but he's not that insensitive and especially not to cute girls. ]