I'm really enjoying the illustration updates. If you want to read the light novel, sidetrack 2 part 2 of the lightnovel is the same chapter as chapter 56 of the manga:
Sidetrack 2 part 2:
http://itslovetranslation.blogspot.com/2017/06/bl-novel-kill-lights-sidetrack-2-part-2.html?m=1
All the chapters:
https://www.novelupdates.com/series/kill-the-lights/