If you buy the premium ebooks from JNC instead of the regular ones from somewhere else, there are bonus stories not part of the catch-up / web version:
(copy-pasted from the Premium Content thread here)
How a Realist Hero Rebuilt the Kingdom
Volume 1: 6 store exclusive short stories
The Little Tanuki Princess of Amidonia
Aisha: Day of Departure
Tomoe's People-Watching Diary
Juna - Better Days Are Coming
What They Wanted to Be
Liscia: Picking an Outfit
Volume 2: 6 store exclusive short stories & a Color Pinup!
Aisha in the God-Protected Forest
Juna and Excel
Ludwin and XXX
Getting Dressed by Liscia
Tomoe and Poncho's Behind the Scenes Work
The Little Tanuki Princess on the Night Before the Final Battle
Volume 3: 5 store exclusive short stories
Aisha and Juna's Secret Pact
Liscia's Happy Family Get-Together
Jeanne and Hakuya's Joint Complaining Session
In the Refugee Camp
Maid Training
Volume 4: 5 store exclusive short stories
Liscia and Aisha's Emergency Conference
Post-Juna
Roroa's Mistaken Order
The Association for Victims of Masters: Now Seeking New Members
Poncho and Serina: A Bizarre Midnight Snacking Session
Volume 5: 5 store exclusive short stories
Program Production Conference
Castor's Marine Diary
The Fiancees' Guarding Techniques
Fried on the Grill Every Day
On a Corner During the Spring Announcement Festival
Volume 6: 8 store exclusive short stories
Tomoe, Holding Down the Fort
Naden and the Royal Capital
Poncho Becomes a Governor
Juna and Roroa Demand Answers
Ruby Goes to Hal’s Family Home
The What-If Known as Discarded Setting Elements
Liscia in Recovery
The Former King and Queen are Enjoying the Slow Life