11화: 아이라, 사이타마 요시미 백굴의 신비한 소리를 조사하다

11

After leaving Nikko, Airi hears a mysterious sound only she can hear. They head to the origins of that sound, to find out that it's the Yoshimi Hundred Caves in Saitama, a historical site. (Source: Crunchyroll)