This simplification was achieved through a process (similar to that of simplified Chinese) of either replacing the onpu (音符, "sound mark") indicating the On reading with another onpu of the same On reading with fewer strokes, or replacing a complex component of a character with a simpler one.
[3] The simplification in shinjitai were only officially applied to characters in the Tōyō and Jōyō Kanji Lists, with the kyūjitai forms remaining the official forms of Hyōgaiji (表外字, characters not included in the Tōyō and Jōyō Kanji Lists).
For example, the character 擧 (KYO, agaru, ageru; raise [an example]) was simplified as 挙, but the character 欅 (keyaki; zelkova tree) which also contained 擧, remained unsimplified due to its status as a Hyōgaiji.
Despite this, simplified forms of hyōgaiji do exist in Japanese character sets, and are referred to as extended shinjitai (拡張新字体).
However, they are to be seen as unofficial, a position reiterated in the National Language Council's 2000 report on Characters Not Listed in the Jōyō Kanji Table.
The Japanese Industrial Standards (JIS) contain numerous simplified forms of Kanji following the model of the shinjitai simplifications, such as 﨔 (the simplified form of 欅); many of these are included in Unicode, but are not present in most kanji character sets.
In both cases the variant character had a different meaning and reading but was adopted due to its lower stroke count anyway.
Similarly, 卒 ("graduate") has been kept unsimplified in isolation, but in compounds has been simplified to 卆, such as 醉 to 酔 "drunk"; 專 has been simplified to 云 in some characters, such as 傳 to 伝 ("transmit"), and 轉 to 転 ("revolve"), but it takes a different form in 團, where instead of changing the phonetic element in a regular manner to get the expected 囩 it is shortened to the meaningless component 寸, producing 団.
The latest 2010 jōyō kanji reform has added additional inconsistencies in this regard as in some instances radicals that were previously uniformly simplified across the jōyō set now first appeared in their traditional variants in some of the new jōyō characters; contrary to prior practice no new simplifications of characters have been carried out, likely in consideration of established JIS character set use spanning decades at this point.
Nevertheless, the guidelines published by the Japanese government explicitly permit simplification in handwriting, and do not object to use of alternate characters in electronic text.
Within the jōyō kanji, there are 62 characters whose kyūjitai forms may cause problems displaying: 海 社 勉 暑 漢 神 福 練 者 都 器 殺 祝 節 梅 類 祖 勤 穀 視 署 層 著 諸 難 朗 欄 廊 虜 隆 塚 祥 侮 僧 免 卑 喝 嘆 塀 墨 悔 慨 憎 懲 敏 既 煮 碑 祉 祈 禍 突 繁 臭 褐 謁 謹 賓 贈 逸 響 頻 These characters are Unicode CJK Unified Ideographs for which the old form (kyūjitai) and the new form (shinjitai) have been unified under the Unicode standard.
Many of the original characters which have become merged are no longer used in modern Japanese: for example, 豫 (YO, arakaji(me); in advance) and 餘 (YO, ama(ri); excess) were merged with 予 and 余, respectively, both archaic kanji for the first person pronoun "I".
However, 芸 poses a problem, in that Japan's first public library, Untei (芸亭) (built during the Nara Period), uses this character.