Those who boot up their Home menu on their JP 3DSes and are connected online will see a message scrolling beneath the splash screen for Taiko 3DS2 prompting a software update from the eShop. It's nothing major; a preparatory update for handling DLC quests, the first of which will be released tomorrow (together with five DLC songs!).
It's 17 blocks large, and without it, you will be unable to play DLC quests, so it's pretty important regardless.
