So I got a copy of the SE and the art booklet contains bonus short stories that I don't believe appear in the LN volumes JNC sells.
Credits are by Roy, edited by Alex Mai
The stories take up 34 pages of the booklet. The booklet itself is 100 pages.
The Duke's Request Takes place immediately after Vol 1 Chapter 1: Episode 3 at the Duke's mansion.
Before They Met Takes place prior to Vol 1 Chapter 1: Episode 4 at Gimul.
Elia's Passion and Her Family's Support Takes place after Vol 3 Chapter 2: Episode 29 slight after the laundromat opens at the inn the ducal family is staying at in Gimul.