She has green yet greyish hair and wears a paper-mask (with a large eye on it) which covers her eyes. She has green eyes and they are revealed occasionally.
She's dressed in a white, traditional Japanese kimono. When she's in her cat form, her fur is black and white.
Since she lives on a tree, she's usually bored. To fulfill her ennui, she is mischievous for a majority of the time. Although, she is rather hotheaded shown when someone rudely yanked a branch off her tree. The youkai finds human horrible creatures when she sees children harassing another. Annoyed by them, she freaked them out by making caterpillars rain on them.
She herself has mentioned that as a youkai, she doesn't understand humans but nonetheless, exhibits concern and remorse, and even prone to tears. She is curious and follows her curiosity and can be described as a tsundere. When Natsume questioned her interest in him mainly because she is bored to which she quickly denies.
She shares Natsume's loneliness but disagrees that being alone is better when he wished he was.
One day, the youkai is bored and attempts to amuse herself by driving away some bullies that were tormenting Natsume, with her true intention actually being to help Natsume. She soon realizes that Natsume can see her and she becomes interested in him.
She constantly teases him until he finally asks her why she cares so much about him. She becomes bashful and embarrassed, replying that she has more important things to do rather than care for humans. Natsume then walks away smiling.
The following day, she scares Natsume and as a result, he falls and causes another boy to fall. Natsume yells that he hates the youkai and tells her to go away.
After that event, Natsume begins taking another road to school even though it's longer. The youkai starts searching for him in the form of a cat and finds him sitting alone in a grassy field. Natsume places her on his lap and they watch the sunset together.
The day after, due to family issues, Natsume moves to another place which saddens the youkai.
Many years later, Natsume returns to see her. She is moved by his return and embraces Natsume. He recognizes that the scent of the Tree Youkai has the same scent as the cat he placed on his lap during his childhood and realizes they were the same person.
- Main article: Takashi Natsume
Though she would probably deny it, she is fond of him and found him interesting as it is rare for her to encounter a human with the ability to see youkai. She had fun scaring the young Natsume but never meant any harm. She felt extreme remorse when she accidentally went too far in her antics which caused him to lash out. At the same time, she didn't have the courage to see him and instead, opted into a cat form to visit the lonely young Natsume. When he gently embraces her in her cat form, she wished to really be cat so that she could stay with him.
Through her interacts with him, she learned that loneliness is a miserable thing. When she heard his wish to be alone, it sadden her to the point of tears.
She misses him and would occasionally think of him after he had moved; hopefully he found happiness. When Natsume came to see her to clear up their misunderstandings she wasted no time in hugging him, overjoyed to see him again.