Bernard?

When Sophia heard what she said, she couldn't help but fall into contemplation what Anna said might be true however, she felt it was also unlikely as well, otherwise, they would have long seen traces of Demon beast around the places, not to mention the fact that it was close to impossible for a demon beast to be able to pass through the steel door.

Even if the demon beast was extremely strong there wouldn't have been any way the demon beast would be able to enter without causing considerable damage to the steel door, this was already considering the fact that the steel door could regenerate due to it being made of out nanomaterial which was one of the strongest material that was truly hard to damage.