Is "Li" a Japanese-made Chinese character or an ancient Chinese character in China?

Because Chinese characters are widely used in Japan, some commonly used Chinese characters with more strokes also have simplified characters. The Japanese character "Jin" you mentioned is one of the simplified characters in Japanese. However, the principle of simplification is not consistent with China's Chinese character simplification scheme. Compared with this character, Japanese simplified Chinese characters "Han" and "Yi" have the same simplification principle.