There have been times in the past where she's been more hesitant with talking about this, but Madoka did start about it - so then she figures it's only fair for her to finish explaining, rather than leaving him hanging. Especially if he actually wants to know.

"Well.. In my world there are these scary creatures called witches. They're like monsters, but nobody knows they exist, even though they lure regular people into their labyrinths and kill them all the time."

Her tone is serious, considering it's such a serious topic. But there's still an edge of that uncertainty born from shyness that Madoka displayed before too in it.

"The only people who know about them and can fight them are magical girls. Those are girls around my age who make a contract with this alien creature called Kyubey. Making a contract means you get to make a wish that'll be fulfilled, but afterwards you'll be obligated to fight those witches." Her gaze drops down, looking at her hands on the table. "But.. a really, really strong witch showed up in the city I live in right before I ended up here on the train. If no one stops that witch, she won't just end up destroying the town and everyone in it, but the whole world.. And other magical girls tried to fight it, but they weren't strong enough."

Madoka shakes her head, looking back up at him.

"Kyubey said that I'd be strong enough to do something about it if I made a contract. S-So I'm going to. I can't just abandon everyone."