Nyanko-sensei is a popular character from the manga and anime series Natsume's Book of Friends (Natsume Yūjin-chō). He appears as a round, chubby cat with a distinct face and a playful personality. Nyanko-sensei is actually a powerful spirit in disguise, serving as a protector for the main character, Takashi Natsume. In the series, Nyanko-sensei often provides comic relief while also offering wisdom and guidance to Natsume. His character embodies themes of friendship and the connection between humans and spirits, making him a beloved figure among fans of the series.