The fourth floor: the Layer of Body and Mind.
Rabbit Girl encountered the "Self of Body and Mind" here—a valiant version of herself dressed in leather armor and a scaled skirt.
What did "body and mind" mean? It referred to every skill that governed the coordination of body and spirit, including martial combat, acrobatics, disguise, tracking, meditation... and so on.
This happened to be Rabbit Girl's strongest field, but it was also the skill she found hardest to break through.
So, she turned to Angel for help again.
But when it came to researching "body and mind," Angel might not necessarily have been stronger than Rabbit Girl. Thus, this time, Angel decided to... seek help from outside.
The person he sought help from was Uncle Ku of the Yingji Race.
More precisely, he first went to Laplace. Laplace happened to have someone nearby who excelled in this sort of skill, and that person was Uncle Ku of the Decaying Flame.
Angel had once seen Uncle Ku outside the All Things House. He had looked like a thoroughly unremarkable figure.
But according to Laplace, his true identity was Vladimir's Time Doppelgänger.
And Vladimir was a Three Stars general, as well as the current supreme commander of the Yingji Race.
Therefore, a few casual pointers from Uncle Ku were enough for Rabbit Girl to clear the stage.
In the end, Rabbit Girl defeated the Self of Body and Mind as she wished. The question she asked was, "Using a Chrono-loop Worm during its sensitive period to track a lifeform that once stayed somewhere, what is the maximum trace-back duration?"
The Self of Body and Mind stared blankly in response.
Rabbit Girl, meanwhile, said calmly, "A Chrono-loop Worm in its sensitive period can trace back as far as one hundred and thirty-eight years