In his search for Nyanko-sensei, Takashi Natsume comes across Mitsumi, a timid and small youkai who has been assigned the duty of "Ishi Okoshi" by his master, the powerful ayakashi Gantetsu. The Ishi Okoshi's job is to wake Gantetsu from his deep sleep. Noticing how sincerely Mitsumi wants to carry out his responsibility, Natsume decides to assist him in completing this task. But time is running short, and others are also trying to rouse the divine being. A mysterious stranger starts showing up at the home of Kaname Tanuma, Natsume's friend. Over several days, this person has brief exchanges with Tanuma and then leaves. Natsume finds out that the visitor is actually a youkai in disguise, who claims to have no harmful intentions. Even though Tanuma trusts this youkai, his health begins to worsen, making Natsume suspect the visitor's true intentions. What is the reason behind this sudden appearance, and what connection does the youkai have with Tanuma?