A Youkai that resides on a tree, located in a path that Natsume used to take when he is walking to school or walking back home back when he was in elementary school. Whenever Natsume comes near the tree, she always suddenly comes off the tree and scare Natsume, he finds it very irritating, but as herself, personally finds it very amusing. The Youkai is always seen by herself, and shows dislike to humans, often calling them rude, selfish and complicated beings. She is always seen attempting to scare people who walk pass the tree, but none can see her, in result. She gets mad occasionally if someone does any harm to the tree, she would do her best to chase them off. She is also able to transform in to a black and white cat, which humans can see.
A "young" spirit who befriends Natsume in the seventh episode of the first season, after being rescued from other yokai, who bullies him due to his gentle and shy nature. Because of this, he takes a great liking to Natsume, who also rejects to have his name for the Book of Friends and instead tells him they are friends. Occasionally he heads off to visit him and due to his inexperience as a spirit needs a potion to turn into a human child for a while. It is implied that his mother has passed as when Kogitsune talks to what is supposedly a grave he refers to it as mom.
Youkai that first appears at episode 6 and 7 of Zoku Natsume Yuujinchou.
The class president of Takashi's class. Sasada believes that Takashi can see spirits, and constantly asks him questions about it, to which he replies that he doesn't have such an ability. Much to Takashi's chagrin, she wants to come along with him when he's visiting spirits. She possibly may have a crush on him in the anime, as she blushed in episode 5 when Takashi asked why she wanted to come with him to an abandoned train station (he was going there to see why Reiko had a ticket for that place). Luckily, he was rescued by Tanuma, who distracted Sasada long enough for Takashi to escape on the bus. The story in the manga differs slightly, as Sasada moves away after the encounter with Shigure, so she has far more spotlight in the anime. (Source: Wikipedia)