The long wait is finally over...in Japan, at least. The Messenger's "Picnic Panic" DLC is going to launch in NA/EU on July 11th, 2019. The same date was given for Japan, which is why the DLC is live right now. They're just a little bit ahead of our schedule!
The Picnic Panic DLC adds in three new levels, new bosses, and more. The best part is, all of this DLC is free!