[And sensing that it's difficult for her to talk about this, he doesn't make her elaborate. He's content with just hearing that.]
Then I suppose it really is better for you to be here. That's no way of living.
[Sighs before he begins to talk about Crona. He really doesn't feel like explaining it, but there's no choice now that she's talked about her experience.]
In all honesty, we should have never trusted the one who used my friends and I. When we first met him he was sided with his mother, a witch who was using him to spread madness throughout our world. When that didn't work she woke up the Kishin instead and had Crona fight us. When Crona lost they came to our school and made us think that they had truly stopped following their mothers evil ways and was becoming friends with us. Crona used that trust to plant something in Ms. Marie so that Dr. Steins madness would take over.