Soul-searching, naturally, would be performed on the soul of the man in black.
The man in black was a cultivator, not a mortal. For a cultivator to search a mortal's soul would go against the Heavenly Dao, but searching a cultivator's soul would merely incur karma. Furthermore, since this man in black was an evil cultivator already at the Tribulation Transcendence Stage, that karma was even less significant.
At worst, it would just mean weathering a few heavenly tribulations and seeing one's cultivation regress a bit.
Chapter 234