Embracing the mandate of the Great King symbolizes the authority of civilization and enlightenment, and Kamiyagawa has officially become a deity.
Upon awakening on this occasion, he indeed felt a sense of transformation.
Previously, the shikigami under Kamiyagawa had become gods, and although they had gained true divinity, their essence did not change. Mary was still Mary, and Hannya was still Hannya.
Kamiya's current feelings are similar; he doesn't feel that his personality has drastically changed after becoming a god.
Moreover, there are precedents of mortals becoming deities within the Takamagahara faction.
The Medicine Seller is an example.
