Kushige is a tsukumogami born from a large chest within Botan Nagatsuki's wedding trousseau, manifesting as an elderly man with white hair and a beard. He possesses a calm, gentle, and wise nature, typically remaining silent and speaking infrequently in a soft, low voice using old-fashioned speech. As a benevolent spirit in the Nagatsuki household, he dedicates his existence to protecting Botan and her home.

His primary ability involves generating potent magical barriers to shield Botan and the residence from threats. This duty consumes nearly all his energy, preventing his participation in other household spirit tasks like sealing malevolent entities. He has been Botan's guardian since her childhood, often serving as her sole companion when other spirits were occupied.

A violent attack on the Nagatsuki residence by a Karakasa tsukumogami severely damages Kushige, nearly destroying him. To survive, he seals his own soul within his original chest form, entering dormancy. This self-sealing abruptly ends his barrier protection, exposing Botan and the home to danger.

Following a conflict involving the Gagakuryo organization, Kushige's soul gradually heals, allowing his revival and return to duty. Post-recovery, he refocuses entirely on Botan's protection, enabling him to participate more actively alongside other tsukumogami in defense. This return marks a shift from his previously passive role, and his speech after revival is noted as a rare occurrence.