A story about in and out of the circles. How do people define a close or distant relationship? Many people often judge others by stereotypes and exclude someone unconsciously. By using the same phrase that “knock knock knock, can I come in?”, the author Nian told us a story of rejection and acceptance. Although the one may look or act differently, it can also be a special and beautiful exist in our world. By using different colors of the circles, and a big wolf’s view as the outsider, the readers shall find more amusing elements in the picture.   Other than Hsin-Yu Sun’s other titles with detail depictions, the illustrations in here is more toward young readers and shall be able to appeal all the kids coming into her world.