So these are the last chapters of the Kagami After Story included in the Kabuto novel.
Overall, it was a pretty interesting read, since it barely focused on the Rider/Worm aspect of Kabuto at all, instead mainly revolving around Kagami’s character. It doesn’t really add much to the story of Kabuto, but it’s enjoyable as a nice little side story. The ending’s kinda bittersweet too.
Kamen Rider Novel Translations 