Karada wa Jidou, Nakami wa Ossan no Nariagari Bokenki - Satera mo Tsuiteikimasu! - Vol. 2 Ch. 9

[MangaDex]

 

[BulbaCPG]

we getting so much more story from the side series than the main one.

 

[Chizan]

Replace 'magic' with 'slaves', and you'll understand why industrial revolution didn't begin with the Romans..