Got it!
He did not hesitate. As soon as he succeeded, he fled a thousand miles away, moving quickly toward the corner of the wall. Then he summoned the Dark Flame for the Nonexistent Beast to swallow, leaped over the sealed wall, and, with a Shadow Leap, he slipped out of the laboratory.
Inside the room, the young man did not notice that something had suddenly gone missing beside him.
It wasn't until ten minutes later, as he casually shifted his position, that he caught a glimpse of the pedestal that should have contained the Wind of All Beginnings from the corner of his eye.
"Hm?"
He paused, stood up, rubbed his eyes, and looked again.
"It... it's gone!?"
His panicked shout echoed through the laboratory, awakening the woman with goat-like eyes.
"What's the matter?" she asked with a frown.