Song Lei had a problem at hand that he had to solve. Kang Mirae needed a place where she could stay.
He had a few criteria on where to pick. First, it had to be near the 14th floor, where he could sense if something was going wrong. Preferably, it would be best if it were inside the range of two floors. Considering that the 13th floor was uninhabitable for now, the 12th floor could be the best choice.
The second one was that it had to be somewhere protected. Kang Mirae was still too weak. Although her ability looked cool and had good effects, she had no real fighting experience. She could freeze up in the face of danger, and that would be her end unless Song Lei was there to help. For this reason, it had to be a room with protection from ethereal beings.