Death's Daughter and the Ebony Blade (Manga) Volume 3 by Maito Ayamine

Olivia sliced and diced her way to a victory for Fernest on the Plains of Ilys. Now, she and her comrades will march on to a new mission: to take Fort Caspar. Though the fort is heavily fortified, and their squadron is only meant to buy some time for the main army to arrive, Olivia doesn't feel like waiting. It's time for Ashton’s budding tactical genius to shine as, at Olivia’s request, he hatches a scheme to take the fort through deception—much to the displeasure of Claudia and her honorable sensibilities. It's a crazy plan, but nothing Olivia can’t pull off with her ebony blade in hand. Meanwhile, within the imperial army, powerful players are beginning to take notice of Olivia’s spree of murder and destruction...