Vol. 35 (Ghost Case) and Vol. 70 (Burning Dog Case) could help understand the trick
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
We're not far from Mount Takao, the Tengu Mountain (vol. 11), and it happens the old priest looks like Mr. Hawk, who looks like a tengu. Funny because tengus are either crow-like or eagle-like. Karasuma is a crow tengu, and Mr. Hawk/Ooka/Momiji's grampa (according to me) is a hawk tengu. Let's hope nothing bad will happen to the crew
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)