Read I Was Planning to Become a Loyal Sword Manga:
Kashumir grew up working as a mercenary to buy medicine for her precious younger half-sister, Aria.On her way home, after completing a mission as usual, she tripped and hit her head, causing her to remember her past life; thus she realized she had been reborn in the world of the novel *The Night of the Fairy*. Her sister was the main character of this reverse-harem romance while she wa more.. s one of the villains causing Aria to suffer hardships.Since there is no way Kashumir would let her precious sister suffer, she vowed to protect Aria until her adoption into the count's family, just like in the novel.But things turned out differently, and even the male lead candidates, who should've been fish in Aria's pond, all ended up becoming obsessed with Kashumir instead, when all she wanted was to protect her lovely sister.