Preemptively posting pic related because the big in-game text won't be enough for some people.
Chapter 19 will be added in 0.7, the 0.6.x builds will add side content.
0.6.0 adds all of Kota's hangouts. To access the new content, load a save from chapter 14 (or onwards) and select the Hang out with staff option, then Kota.
There are five hangout scenes, and a special episode that plays at the end of chapter 17 if you completed all of them to cap Kota's story.