Under the Hole!

Ban landed smoothly under the crack with only a little shake on his knee. He recovered a while later and he then waved the lamp to illuminate and observe his surroundings. 

He noticed that the area under the crack was actually spacious. The space was spherical in shape and on closer look, Ban could tell that it somehow resembled a huge tube. 

He looked at the front and the back alternatively to determine where he should go. The soil or the platform he was standing on right now was a little damp. Ban also took notice of the streams of dark water flowing right beside him smoothly. 

Ban observed more and after a little while, he finally managed to find a clue left by the Two-Tailed Rats. There was a clump of brownish fur, flowing alongside the dirty water. Ban no longer thinks about anything as it was already obvious where the other Two-Tailed Rats are.