The Coppersmith’s Bride (2020)

Blurb:
Shiina, a freshman in college, is enjoying a cozy life in Niigata Prefecture dating her coppersmith boyfriend, Shuu. She’s grown used to the rhythmic sound of his hammer, inwardly dubbing him the “smithing nut” for his obsession with hunkering down in the workshop, even on his days off.

What she’s not ready for is a sudden proposal out of nowhere! Barely out of high school, is she ready for the next step? And more importantly, can she really hack marrying into a prestigious smithing family?!

Source: www.anisearch.com/manga/59670