Like Kouichi, she's an immortal cat that wants to die.
Shijima Kurookano is originally a cat that is created by the former holder of Shinra Banshou, a medical practitioner during the Edo Period. The doctor used Shinra Banshou's knowledge to give a human heart to a cat, made her immortal. She's at least a century and a half years old and has been since Miharu's birth. Both Shijima and Aizawa are referred as the Hakutaku. She's voiced by Kei Shindou in Japanese and Cherami Leigh in English.
Shijima learns the kinjutsu "Tenpenka" to become a human. Shijima has a pair of yellow eyes and white hair. When she walk, usually she puts her hands in front of his body and her body looks rather bent. When in not in the human form, Shijima is disguised as Miharu's cat, Shiratama. She is quite similar in appearance to the spirit of Shinra Banshou.
She's first seen as an Alya student and acts as a protagonist. She's entrusted to keep the Toga's village kinjutsusho, Daya. After the principal dies, she gives it to Miharu. She's actually in Kotarou Fuma's side (because he trust him and he learnt Tenpenka from him), but after knowing Fuma's desire, she choosese to be with Miharu. After Shinra Banshou appear, she decides to follow her, and disappear, together with Kouichi.