Konyaku Haki sare Suterareru Rashii node, Gunjin Reijou Hajimemasu

Celestia, a young lady from a noble family, hears a prophecy from her stepsister, who calls herself the "heroine." "Your engagement will be broken off, and your father will abandon you. In the end, you will go to a convent." To avoid the future of ruin that is unwillingly becoming reality, Celestia becomes an apprentice to her grandfather, a great military leader in the frontier! She resolves to live strongly as a soldier!

(Source: Kadokawa, translated)