Notetsu is a bat-shaped netsuke tsukumogami with purple hair and violet eyes in his spiritual form. He resides at a rental shop in Edo-period Japan, where objects gain sentience after a century of existence.

His background involves prolonged mistreatment by humans. Initially cherished by an owner who cared for him meticulously, he was sold to settle debts following the owner's son's business failure. This abandonment led to repeated resale among multiple owners before he reached the rental shop. Consequently, he forged a deeply cynical worldview, believing humans value objects solely for utility before discarding them without sentiment. He frequently expresses harsh judgments toward humans, reflecting his resentment over being treated as disposable.

Within the rental shop, Notetsu distinguishes himself through mobility and initiative. As the only tsukumogami capable of flight, he autonomously gathers information, often eavesdropping on human conversations during lending assignments. He participates in gossip with other tsukumogami while maintaining a critical stance toward their human caretakers.

In the first episodic mystery involving a missing mouse-shaped netsuke, Notetsu plays a pivotal role. He volunteers to investigate Edo's red-light district, leveraging his ability to navigate discreetly and retrieve the lost item. Through this case, he witnesses the siblings' genuine appreciation for the tsukumogami's assistance, contrasting with his prior experiences of human neglect. This exposure initiates subtle development in his perspective, reducing his distrust while acknowledging that some humans may value objects beyond mere functionality. His actions demonstrate a capacity for dedication despite underlying skepticism about human-object relationships.