It was invented by physicist Aikitsu Tanakadate (田中館 愛橘 Tanakadate Aikitsu) in 1885, and postdates the Hepburn system of romanization. Tanakadate's intention was to completely replace the traditional kanji and kana system of writing Japanese with a romanized system, which he felt would make it easier for Japanese people to compete with Western countries. Since the system was intended for Japanese people to use to write their own language, it is much more regular than Hepburn romanization, and, unlike Hepburn's system, it makes no effort to make itself easier to pronounce for English speakers.
Nippon-shiki was followed by another, similar system, Kunrei-shiki. The difference between Nippon-shiki and Kunrei-shiki is the difference between the kana syllabary and modern pronunciation. In modern standard Japanese, the sounds of the pairs di/zi ぢ/じ, du/zu づ/ず, dya/zya ぢゃ/じゃ, dyu/zyu ぢゅ/じゅ, dyo/zyo ぢょ/じょ, wi/i ゐ/い, we/e ゑ/え, kwa/ka くゎ/か, gwa/ga ぐゎ/が have become identical. For example, the word kanadukai (Nippon-shiki) かなづかい is pronounced as kanazukai in modern Japanese.
Nippon-shiki is considered the most regular of the romanization systems for the Japanese language, because it maintains a strict "one kana, two letters" form. Because it has unique forms corresponding to each of the respective pairs of kana homophones listed above, it is the only system of romanization that allows lossless ("round trip") mapping; see the hiragana article for more details.
Nippon-shiki has been established by the International Organization for Standardization in the ISO 3602 strict form. The JSL system, which is intended for use instructing foreign students of Japanese, is also based on Nippon-shiki.
|あ/ア a||い/イ i||う/ウ u||え/エ e||お/オ o||(ya)||(yu)||(yo)|
|か/カ ka||き/キ ki||く/ク ku||け/ケ ke||こ/コ ko||きゃ/キャ kya||きゅ/キュ kyu||きょ/キョ kyo|
|さ/サ sa||し/シ si||す/ス su||せ/セ se||そ/ソ so||しゃ/シャ sya||しゅ/シュ syu||しょ/ショ syo|
|た/タ ta||ち/チ ti||つ/ツ tu||て/テ te||と/ト to||ちゃ/チャ tya||ちゅ/チュ tyu||ちょ/チョ tyo|
|な/ナ na||に/ニ ni||ぬ/ヌ nu||ね/ネ ne||の/ノ no||にゃ/ニャ nya||にゅ/ニュ nyu||にょ/ニョ nyo|
|は/ハ ha||ひ/ヒ hi||ふ/フ hu||へ/ヘ he||ほ/ホ ho||ひゃ/ヒャ hya||ひゅ/ヒュ hyu||ひょ/ヒョ hyo|
|ま/マ ma||み/ミ mi||む/ム mu||め/メ me||も/モ mo||みゃ/ミャ mya||みゅ/ミュ myu||みょ/ミョ myo|
|や/ヤ ya||ゆ/ユ yu||よ/ヨ yo|
|ら/ラ ra||り/リ ri||る/ル ru||れ/レ re||ろ/ロ ro||りゃ/リャ rya||りゅ/リュ ryu||りょ/リョ ryo|
|わ/ワ wa||ゐ/ヰ wi||ゑ/ヱ we||を/ヲ wo|
|voiced sounds (dakuten)|
|が/ガ ga||ぎ/ギ gi||ぐ/グ gu||げ/ゲ ge||ご/ゴ go||ぎゃ/ギャ gya||ぎゅ/ギュ gyu||ぎょ/ギョ gyo|
|ざ/ザ za||じ/ジ zi||ず/ズ zu||ぜ/ゼ ze||ぞ/ゾ zo||じゃ/ジャ zya||じゅ/ジュ zyu||じょ/ジョ zyo|
|だ/ダ da||ぢ/ヂ di||づ/ヅ du||で/デ de||ど/ド do||ぢゃ/ヂャ dya||ぢゅ/ヂュ dyu||ぢょ/ヂョ dyo|
|ば/バ ba||び/ビ bi||ぶ/ブ bu||べ/ベ be||ぼ/ボ bo||びゃ/ビャ bya||びゅ/ビュ byu||びょ/ビョ byo|
|ぱ/パ pa||ぴ/ピ pi||ぷ/プ pu||ぺ/ペ pe||ぽ/ポ po||ぴゃ/ピャ pya||ぴゅ/ピュ pyu||ぴょ/ピョ pyo|