He is a short, slim man with black hair, dark brown eyes.
A shy, quiet and hard-working man, Japan doesn't know very much about the outside world and needs time to adjust to other people. But he's very curious and interested in learning things from other nations. His distinct island customs may seem mysterious to others, although he finds them perfectly normal. He tends to have the behavior of an "old man" and was a hikkomori for a long time (Japan had spent about 250 years in isolation). Though he appears horrified at the idea of nudity or intimate contact, he has erotic woodcuts in his possession, which he tries to hide secretly between his non-erotic books. Japan also voiced his preference for 2D girls over 3D girls to England, Greece and France in one strip, hinting that he has an otaku side.
He loves animals, especially cats, and owns a white dog called Pochi. He also eventually gets a rabbit and a guinea pig. He tends to have a weakness for things that are soft and fluffy.