Devil does have a novel! It's written by a famous bl novel and webtoon writer Moscareto! They have written many things like the novels of The new employee, March and Willow love/romance and the webtoons of Punch drunk love and You and I can't do this! Im not sure if there is an English fantranslation around since it's quite complex to translate but you could do your own mtl if you're really curios and don't mind mtl!
flip the script mentioned!(oww my headache) and yeah this has a novel like mentioned above!!
OH MY GOODNESS!!! I've read some of those novels! I just never look at the author Thank you so much for this info! May Ra bless you! ヾ(☆▽☆)
A headache indeed xxx
No one even mentioned the novel so I guess there's none... and it's probalby an original story like Flip the Script ╥﹏╥