The Japan-only 9.1.0-20J system update was released on October 10(11 in Japan), 2014.
See here for the Japanese changelog. Among other things, this added theme support to the JPN Home Menu.
The following titles were updated: Home Menu and CVer.
The version of JPN-region New3DS application title 000400102002CA00 listed in SOAP was changed to v0, originally this title was added under SOAP with the Oct 2 JPN-only "update" as v1. Note that this title wasn't actually changed, the TMD is identical besides the title-version. Both versions of this title already existed.
System update report: