[He watches her roast the marshmallow over the fire, then when she indicates for him to mimic her, he follows her lead. Carefully, he turns his stick around, making sure the treat is evenly roasted on all sides. He's quite good at cooking.]

There are many beings who can use elemental powers without a Vision, but humans are not one of them. There is... a kind of technology that allows that, though. [He pauses, unsure if he should go into details about gods, wars and Delusions that one of the nations produces. Maybe she'll find out about it eventually, if she ever sees Childe using his.] It's really not a good idea to use it, because of the negative effects it can have on you.

[He's trying very hard not to remember Teppei and many others who lost their life because of Delusions.]

As for one person having multiple Visions... Each person gets one Vision as far as I'm aware, but I know someone who managed to use two at the same time, if only for a short moment.

[A moment that saved Aether's own life.]