Description
Japan appears as a short, slim man with black or dark brown hair and dark brown eyes that became a lighter shade and less void-like in later portrayals. He typically wears a white naval uniform with black and gold accents, adopting a more ornate version with gold epaulets and frog clasps for formal events. A katana rests at his left hip. His height varies visually relative to other characters, sometimes reaching America's chest and other times near eye level. He occasionally wears black-framed glasses.

His personality is shy, quiet, and hard-working, often seeming like an "old man" due to his long history. Distinct island customs and nearly 250 years of self-isolation left him inexperienced with the outside world, requiring significant cultural adjustment. While curious about learning from other nations, he typically refrains from speaking to "sense the mood." He experiences culture shock but gradually adapts. An otaku side emerges in his preference for "2D girls over 3D girls," buying Shonen Jump, and playing video games. He is horrified by public nudity or intimate contact yet secretly possesses erotic woodcuts hidden among books. He enjoys food, especially Japanese cuisine, and expressed dismay over rising egg prices. He intensely dislikes cockroaches and rarely shows anger, usually summoning only an "unpleasant feeling." He loves animals, particularly cats, and owns a white dog named Pochi (resembling an Akita or Shiba Inu), a rabbit, and a guinea pig, revealing a weakness for soft, fluffy things. Tranquil hobbies include bonsai cultivation, cleaning, gazing, walking, drawing manga, and making soba. Though he lost the ability to see and communicate with mystic spirits, he remains deeply respectful of deceased spirits and fears provoking them.

Found as a young boy by China, who cared for him and taught kanji, Japan adapted the script to create hiragana. He did not view China as a brother; their relationship strained over differing views and Japan's vow to "become stronger," culminating in Japan attacking China with a katana and leaving a disfiguring scar on China's back. Japan then isolated himself for about 250 years, maintaining contact only with the Netherlands, through whom he learned of America's impending arrival. America forced Japan to open his borders; Japan later confessed his fears about interacting with others, leading America to reassure him with a "table-turning" prank that eased his adjustment. Post-isolation, Japan caught up on world events, formed friendships, and eventually joined the Axis alliance with Germany and Italy. His spiritual disconnect is noted alongside efforts to prevent other nations from disturbing spirits.

Relationships are complex. With America, he bonds over technology and video games, collaborating on creations like a game where collecting colored hamburgers unlocks bunny ears. Japan calms America with unique techniques like offering mysterious candies and often sides with America's decisions despite finding him difficult. Cultural differences are frequent. Lingering tension exists with China from their past conflict, though Japan occasionally shows protective instincts, like warding Russia away. Korea antagonizes him, plagiarizing his style and obsessively grabbing his chest while claiming historical grievances. Germany and Japan work efficiently as Axis allies, though Germany admits difficulty understanding Japan's thoughts; Japan admires Germany's productivity and gave him cakes after cleaning. Italy unnerves Japan with affection, prompting Japan to demand marriage after unwanted kisses, but mutual respect develops for each other's art and history. England and Japan form the Anglo-Japanese Alliance based on shared loneliness and tea appreciation, with England aiding Japan's reintegration. Greece shares a friendly bond over cats, culminating in an implied intimate encounter dismissed by Japan as a dream. Japan despises Russia due to the Russo-Japanese War's financial strain, attempting revival tactics like caltrops or harpoons without success. He is close to Osaka for diplomatic support and maintains a long-standing companionship with the Netherlands from his isolation era. Prussia visits often for tea and manjuu, their "near inseparable" relationship including Japan helping him clean until exhaustion.

Development across media shows progression from isolation to engagement. Initially reclusive and culturally inexperienced, he gradually forms alliances and friendships. His interactions reflect historical events like economic struggles or wartime collaborations, while modern strips depict cultural exchanges and shared hobbies. The OVA "Netherlands and Isolationist Japan" explores his trade companionship during isolation.