Post-main title, Yoki has survived and is an adult, cared for by his adoptive mother, the beautiful, silver-haired Nui (Makiko Esumi). She is a mushishi (bugmaster), an expert in controlling mushi, "the phantom soul of nature breathing inside every living thing...and the dead," per an intertitle.

Mushi are basically tiny bugs with fluorescent tentacles, like something on a coral reef, that can slide in and out of people's bodies.
Yoki, now called Ginko (Joe Odagiri), shows off his own de-bugging smarts when the owner of an inn (Lily) asks him to examine her staff and he correctly diagnoses an infection by the Wn of the Ah-Wn bug (script has a lot of such gobbledygook).

She also asks him to look at her young granddaughter, Maho (Reia Moriyama), who's growing horns on her forehead.