In episode 27 of Ushio to Tora (2015-16 version), we come to learn that Hakumen no Mono has used memory-altering hiyou to make almost everybody forget about Ushio and Tora (Jie Mei, Saya, Hyou, and Tokisaka/Tokijun are spared for various reasons).
In particular, in episode 27, we specifically see Kirio having lost his memories of Ushio and Tora. Then, in episode 29 (he doesn't appear in episode 28), we see that he's regained his memories of the two of them.
How did that happen? (The anime seems to be eliding a bunch of details in order to fit the rest of the story into this cour, and this seems like one of those things that would've been cut.)