Tang Shaoyang brought the demon swordsman to his father-in-law. He told the old man everything about Zaneos' background, hiding nothing from the old man even though Zaneos was a demon. Earth lacked history with demons aside from the fiction where all demons were bad. Of course, the old man had a different vision than those people in the fiction or the people of other worlds with demons in their history.
Kang Jiayi accepted Zaneos with a welcome hand. The old man did not have a prejudice against the demon. In fact, the old man was excited when he heard the demon could also teach sword techniques. Zaneos was willing to share his technique with TEIS. The old man also willingly offered a high rank in TEIS, but the demon rejected.