I'm the Commander of the Second Male Lead's Knights

After a monster attack kills her family, Nina is sold to House Louvoirennais, where she meets Adrian—a tragic secondary lead destined for abuse, betrayal, and death. Determined to rewrite his fate, Nina becomes his friend and protector. As she rises through the ranks of the Black Knights, her simple plan is to save the sub-lead. But when Nina accidentally summons a powerful elemental named Sol, she realizes her destiny may be greater than just saving Adrian... She might have to save the world. Source: Tapas