Slightly simplified depiction of the relationship between various JIS character encodings, their standards, their variants on PC platforms, the WHATWG encoding standard, ISO 646 and 2022 and Unicode. Names used are descriptive and are mostly not standard labels. Common subsets of encodings are listed even if not themselves defined by any specification.
Incomplete list of sources consulted:

https://www.itscj.ipsj.or.jp/iso-ir/229.pdf
https://www.itscj.ipsj.or.jp/iso-ir/233.pdf
https://encoding.spec.whatwg.org/
ftp://ftp.software.ibm.com/software/globalization/gcoc/attachments/CP00300.pdf
https://www.iana.org/assignments/character-sets/character-sets.xhtml
The output of Python 3.5's shift_jis_2004, ms-kanji, euc-jp, euc-jis-2004 codecs
The README accompanying source of the same: https://github.com/python/cpython/blob/master/Modules/cjkcodecs/README
http://www.ecma-international.org/publications/standards/Ecma-035.htm
http://x0213.org/codetable/index.en.html
ftp://ftp.software.ibm.com/software/globalization/gcoc/attachments/CP00897.txt
https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP932.TXT
https://www.zophar.net/pc98/anex86.html , specifically the font bitmap for NEC PC98. Cross reference with this PC98 font from here (extracted graphic).
https://web.archive.org/web/20000131063242/http://www.opengroup.or.jp:80/jvc/cde/appendix-e.html
Various ICU mappings, both in online explorer and UCM formats.
See [1] for a code-point by code-point comparison I generated from various mapping definitions from Unicode, ICU and various other places.
Own work
User:HarJIT