Noun
kokuji (plural kokuji)
Any of the kanji characters invented in Japan.
If a character appears earlier in the Chinese literature, it is not considered a kokuji even if the character was independently coined in Japan and unrelated to the Chinese character (meaning "not borrowed from Chinese"). Source: Internet
Another example is 搾 main, which is sometimes not considered kokuji due to its earlier presence as a corruption of Chinese 榨 main. Source: Internet
Another is the kokuji 峠 (mountain pass) made from 山 (mountain), 上 (up) and 下 (down). Source: Internet
However, 鮟 main is not considered kokuji, as it is found in ancient Chinese texts as a corruption of 鰋 main (魚匽). Source: Internet
In other words, kokuji are not simply characters that were made in Japan, but characters that were first made in Japan. Source: Internet
鱇 main is considered kokuji, as it has not been found in any earlier Chinese text. Source: Internet