She may be blushing just a tiny bit when he says the formality isn't necessary. Madoka really hopes she didn't offend him by accidentally being too polite, after all!

But she does listen to what Lea says, slowly nodding along, a curious gaze in her eyes.

"I see.. So it's like a sword and a key at the same time..?" That's what she's getting from that explanation. It makes its name make sense too. "Do you have those because there are a lot of things to unlock where you come from?"

Or is it just a convenient way to ensure you never lose your house keys.

She'd believe it.