Small letters of Kana (a general term for Hiragana and Katakana scripts) are often used to extend the syllabic system to denote exotic or corrupted sounds, such as gemination, diphthong, contraction, and closed syllables. Although Unicode already has 12 Hiragana small letters and 28 Katakana small letters, the following small letters not collected yet remain:

The Hiragana counterparts of the 16 Katakana phonetic extensions
Letters for labialization, nasalization, and palatalized consonants

Phonetic extension system of Kana

Phonetic usage of small Kana is classified into two types: syllabic modifiers and consonants. Syllabic modifiers are attached to basic Kana and form complex syllables: キョ [kʲo] is a syllable composed of the syllabic キ [kʲi] and the modifier ョ (modifying [□ʲi] to [□ʲo]). On the other hand, consonants are immune from other letters: カㇷ゚[kap] (the Ainu word for skin) is consist of the syllabic カ [ka] and the consonant ㇷ゚ [p].

Small Kana used as syllabic modifiers

Classification of syllabic modifiers

Modification	Small Kana letters	Examples
Palatalization	ャ, ィ, ュ, ェ, ョ	キョ [kʲo], ティ [tʲi], チェ [t͡ɕe]
Labialization	ァ, ィ, ゥ, ェ, ォ (ヮ, ヰ, ヱ, ヲ)	クィ (クヰ) [kʷi]
Aspiration	ㇵ, ㇶ, ㇷ, ㇸ, ㇹ	クㇸ [kʰe]
Nasalization	ン	ンガ [ŋa], ンデ [ⁿde]

Small Kana used as consonants

ク [ku] vs ㇰ [k], シ [ɕi] vs ㇱ [ɕ]

Ambiguity

There are some ambiguous cases depending transcription methods: トㇹ may denote [tʰo] or [toh] and クㇲ may denote [kˢu] or [kus]. One way to disambiguate them is to use either of the methods exclusively. Small Kana in Japanese are mostly syllabic modifiers because Japanese language hardly have closed syllable. Consonants are used for more precise transcription for languages which have closed syllable, such as Ainu or Latin.

Proposed characters

Hiragana counterparts of the 16 Katakana phonetic extensions

The Hiragana counterparts of the 16 Katakana phonetic extensions (ㇰㇱㇲㇳㇴㇵㇶㇷㇸㇹㇺㇻㇼㇽㇾㇿ)

くしすとぬはひふへほむらりるれろ (16 characters)

Historic letters for labialization

ゐゑをヰヱヲ (6 characters)

A letter for nasalization

ん and ン (2 characters)

Letters for palatalized consonants

Hiragana き[kʲ]せ*[sʲ]ち[t͡ɕ]て*[tʲ]に[nʲ]み[mʲ] and Katakana キセチテニミ (8 characters)

(*) セ and テ are used with イ (セイ[sʲi], テイ[tʲi]).

Character Properties

XXXXX;HIRAGANA LETTER SMALL KI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL KU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL SI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL SU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL SE;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL TI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL TE;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL TO;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL NI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL NU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL HA;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL HI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL HU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL HE;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL HO;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL MI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL MU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL RA;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL RI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL RU;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL RE;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL RO;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL WI;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL WE;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL WO;Lo;0;L;;;;;N;;;;;

XXXXX;HIRAGANA LETTER SMALL N;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL KI;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL SE;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL TI;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL TE;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL NI;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL MI;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL WI;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL WE;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL WO;Lo;0;L;;;;;N;;;;;

XXXXX;KATAKANA LETTER SMALL N;Lo;0;L;;;;;N;;;;;

Evidences

Hiragana Letter Small Su

Figure: くすしぱ゠とぅ, くすー゠てぃ

小川晋史編『琉球のことばの書き方―琉球諸語統一的表記法』くろしお出版 (2015) p. 176

urn:isbn:978-4-87424-675-7

Katakana Letter Small Ti

Figure: ㇷアチエㇺ

天主公教会編『公教会聖歌集祈祷文』光明発行所 (1920)

http://dl.ndl.go.jp/info:ndljp/pid/962079/58

Figure: チエリ゚ㇳウㇺ, ドウㇽチエデイネ

光明社編『公教聖歌集』光明社 (1938)

http://dl.ndl.go.jp/info:ndljp/pid/1111094/121

Figure: シチャー, シチ

大学書林編集部編『露西亜語基礎1500語』大学書林 (1935)

http://dl.ndl.go.jp/info:ndljp/pid/1080399/34

Katakana Letter Small Te

Figure: ミセリコㇽデイア, テイメンテイブㇲ

天主公教会編『公教会聖歌集祈祷文』光明発行所 (1920)

http://dl.ndl.go.jp/info:ndljp/pid/962079/58

Figure: ホㇲテイア, デイㇲ, ㇲテイウㇺ, ホㇲテイリ゚ア

光明社編『公教聖歌集』光明社 (1938)

http://dl.ndl.go.jp/info:ndljp/pid/1111094/122

Hiragana Letter Small Mu

Figure: むー, むた, みむ, あむ, むめぴ

小川晋史編『琉球のことばの書き方―琉球諸語統一的表記法』くろしお出版 (2015) p. 234

urn:isbn:978-4-87424-675-7

Hiragana Letter Small Wi

Figure: くゐ, ぐゐ, くゐー, ぐゐー, くゐーん, ぐゐーんつす, クヰ

上田万年, 松井簡治共著『大日本国語辞典』卷五富山房 (1941)

http://dl.ndl.go.jp/info:ndljp/pid/1870727/501

Katakana Letter Small Wi

Figure: クヰャウ

諸橋轍次, 鎌田正, 米山寅太郎共著『広漢和辞典索引』大修館書店

Figure: ヴヰオリン

H. C. アンデルセン著, 滝沢譲訳『小説寂しきヴヰオリン弾き』厚生閣書店 (1926)

http://dl.ndl.go.jp/info:ndljp/pid/1019842/2

Figure: セルヴヰア

南方熊楠『続南方随筆』岡書院 (1926)

http://dl.ndl.go.jp/info:ndljp/pid/981768/66

Hiragana Letter Small We

Figure: くゑ-そく, くゑち, ぐゑん, くゑん-えい, くゑん-じゃう, くゑん-ぞく, くゑん-ぱい

上田万年, 松井簡治共著『大日本国語辞典』卷二, 富山房 (1941)

http://dl.ndl.go.jp/info:ndljp/pid/1870644/217

Katakana Letter Small We

Figure: 藤田チヱリー豆総本店

Company name

http://www.fujita-cherrymame.com/

Figure: クヱン, グヱン, クヱツ, クヱチ

諸橋轍次, 鎌田正, 米山寅太郎共著『広漢和辞典』大修館書店

Hiragana Letter Small Wo

Figure: びっくうをーす氏

野津正忠『理論応用計算尺精義』丸善 (1917)

http://dl.ndl.go.jp/info:ndljp/pid/954748/233

Figure: さいふをん

田丸卓郎『中等教育物理学講義』東京開成館 (1930)

http://dl.ndl.go.jp/info:ndljp/pid/1448041/102

Katakana Letter Small Wo

Figure: フヲッグ氏

J. ヴェルヌ著, 川島忠之助訳「新説八十日間世界一周」上『現代日本文学全集』改造社

http://www.let.osaka-u.ac.jp/~okajima/uwazura.html

Figure: ポヲ, Figure: ンモアソヲ

台湾総督府編『台日大辞典』上・下巻 (1932)

http://dl.ndl.go.jp/info:ndljp/pid/1218326/15

http://dl.ndl.go.jp/info:ndljp/pid/1218365/1050

Hiragana Letter Small N

Figure: 中ん谷

Location name

http://net.jmc.or.jp/saishiki/MF_SearchSampleDigitalMapEX2.asp?cntLat=32.81513&cntLon=131.4461

Katakana Letter Small N

Figure: ほゥてよン

柴田流星『残されたる江戸』洛陽堂 (1911)

http://dl.ndl.go.jp/info:ndljp/pid/764342/59

Figure: サンンㇰティシマ, サンクチシマー

アンリ・ドマンジエル編『公教聖歌』玟瑰塾 (1911)

http://dl.ndl.go.jp/info:ndljp/pid/825378/15

Figure: ハマンデカレダ, ハマンデエデ

小林好日『東北の方言』三省堂 (1944)

http://dl.ndl.go.jp/info:ndljp/pid/1871336/68

Bibliography

Katō, Nozomu. Report of Phonetic Kana Usage for Lingua Latina, L2/10-153, 2010. http://www.unicode.org/L2/L2010/10153-lingua-latina.pdf
Ogawa, Shinji (ed.). Ryūkyū-no Kotoba-no Kakikata: Ryūkyū-shogo Tōitsu-teki Hyōki-hō [How to Write Languages of Ryukyu: The Unified Transcription of Ryukyuan Languages], Kuroshio Shuppan, 2015. urn:isbn:978-4-87424-675-7
qvarie, Hatsuon-hyōki-yō Kogaki-kana - Sekai-no Tokushu-moji Wiki [Small Kana for phonetic transcription - Special characters in the world Wiki], 2016-05-12. http://seesaawiki.jp/w/qvarie/d/%c8%af%b2%bb%c9%bd%b5%ad%cd%d1%be%ae%bd%f1%a4%ad%b2%be%cc%be

Acknowledgement

このドラフトの作成にあたり、以下のツイートの提供を受けました。

https://twitter.com/pleist/status/730416940229873664

https://twitter.com/na4zagin3/status/730418863515435008

https://twitter.com/Umihotarus/status/730423680493191169

https://twitter.com/na4zagin3/status/730423898441842688

https://twitter.com/mashabow/status/730431459425554432

https://twitter.com/na4zagin3/status/730434298260508672

https://twitter.com/JUMANJIKYO/status/730432277734268929

https://twitter.com/JUMANJIKYO/status/730439109928345600

https://twitter.com/mashabow/status/730441216353931264

https://twitter.com/sarasvati635/status/730513775548235776

https://twitter.com/sarasvati635/status/730524631744970753

https://twitter.com/sarasvati635/status/730525016295542788

https://twitter.com/qvarie/status/730530664794071041

https://twitter.com/qvarie/status/790187925312909313

また、ドラフト編集に以下の方の協力も得ました。

酒本典明さん

David Corbettさん