It was an update that was released for Japan nearly 3 months ago, though just now was released for the NA/EU versions of Kobuto V.
The main features include:
-a voice pack that makes character voices become 'yukkuri'-ish
-DLC for a theme that includes chibi character skins (that can be found in the Store page)
-character balance changes (managed through the "regulation file" system)
-the ability to record video clips on Switch
Here's the original (JP) source for the patch notes by the developer: https://www.cubetype.com/465
Also, with the update, I think it's worth mentioning that there is no more region locking from those who have the JP version of Kobuto V in online play. The game's online is still relatively populated on Switch in Japan (although so far, I've found that a good number of the JP players were quite experienced), so you can try it out if you didn't get a chance to connect to players online due to the region locking that occurred when the patch was released for Japan (on 12/21/17).
Currently an internet lurker.