I think what you mean by ASCII code for Japanese is the equivalent of SBCS (Single Byte Character Set) in Japanese. For the Japanese, you only have MBCS (Multi-Byte Character Sets), which has a combination of single-byte characters and multi-byte characters. Thus, for a Japanese text file stored in MBCS, you have non-Japanese characters (English letters and numbers, as well as regular non-alphanumeric characters) stored as one byte, and Japanese characters saved as two bytes.
Assuming you don't mean UNICODE , which is a uniform DBCS (character set with two bytes), where each character has exactly two bytes. In fact, to be more correct, recently UNICODE also has several DBCS, because the character set can no longer accommodate another character. Some UNICODE characters consist of 4 bytes, already having the first two bytes as the leading character.
If you mean the first (MBCS), which, and not UNICODE, then there are many Japanese characters, such as Shift-JIS (more popular). Therefore, I suggest you look for the Shift-JIS character map. Although there are other maps of the Japanese character set besides Shift-JIS.
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