An anthology manga about the castles of Japan.

https://www.cmoa.jp/title/298451/ The count’s daughter, Liligen, grieving deeply over her mother’s death, suddenly has a flash of memory from her previous life. She realizes that she has been reborn into the world of her absolute favorite novel, a world she adored so much that she collected all the setting materials, illustration books, and even watched the anime adaptation. But then she notices something shocking. In this world, she isn’t the villainess, but rather a mob character! The illegitimate half-sister of the villainess. Images of the novel’s story race through her mind like a kaleidoscope, showing her where her fate is headed… Yes, a future where she’s continually mistreated by her family, and in the end, forced to take responsibility for a fallen noble house and care for her feeble, ailing father, just as the family stands on the brink of ruin. —Absolutely not! That’s way too awful! Upon awakening with her memories from her past life, she discovers a new power: healing magic. “This power, more than for anyone else, it’s for my dear brother, Theobald!” Determined to defy her miserable fate, Liligen chooses to save Theobald and the frontier lands from a massive monster invasion rather than await her family’s downfall. Abandoning her home, she hurries to her uncle, Margrave Ashgile, where she finds her cousin, Theobald, on the brink of death after exhausting his magical power…?! A faint feeling in her heart awakens a mad, all-consuming love. Once caught, there’s no escape! Love wrapping love, accelerating into passionate devotion! A sweet, melting, honey-colored pure romance where affection overflows and hearts are bound together.