https://musicbrainz.org/doc/Work#cite_note-2

In the “eternal database” table on the “Doc: Work” page, there is a row that reads “Search engine provided by e-License | Japan | Does not seem to contain ISWCs.” However, this database is no longer active. e-License merged with another company in February 2016 and became NexTone.

This is the search portal for the NexTone database, (ISWCs are still not contained)
https://search.nex-tone.co.jp/

The NexTone ID itself has already been updated in ticket STYLE-1210, but this change has not been reflected in the documentation.