They didn't know if the other invader was a friend or a foe, but given the restrictions of that universe, it was more likely someone there due to internal strife among the rebels than an unknown ally.
However, wherever that other invader was, it was bound to have valuable information.
Thus, the whole group managed to track him down, and Shiba discovered the hidden chamber. It was so well hidden that without prior knowledge of it or at least the Minor Dimensional Divinity, it wouldn't be discovered easily.
The Brainwashing God had been in the hidden dimension before, and he had invited to that room once by Pavel, so he knew the place from the beginning. However, at that time, there was a lot of information registered about experiments of Lesta and Pavel.
"Why have the documents disappeared? Have they moved them recently? Do I have such bad luck?"
Those words were clearly heard by Shiba's group. They had just opened the door of the hidden chamber.
