Madougushi Rize, Kaigyou shimasu

Liz is a young girl always dreaming of becoming a great magical tool maker, but she has spent her life working as a slave in her family's shop, barely getting enough to eat. Her older sister Artemesia has claimed Liz's achievements as her own and gained the admiration of the crown prince—eventually becoming his fiancée. After preparing the formal attire for the engagement ceremony, Liz collapses from exhaustion. When she awakes, she finds herself face-to-face with a famous duke known for his magical prowess. He is impressed by her talents and praises her for being a legendary magical tool maker. To help her break free from her cruel family, he proposes a fake engagement...!? (Source: Overalap, translated)