Shinwa Densetsu no Eiyuu no Isekaitan - Volume 10, Chapter 1 – Wriggling Darkness, Part 3

Aliandra Amariel loved magic, dedicating her academic years to the study of runes and spells, pushing the boundaries of mana's infinite possibilities. Like most Fae, her destiny seemed clear until that fateful day of her Class Trial, when the Blind Lich unleashed an undead apocalypse on her home, the fabled underground city of Dal’mohra, and triggered The Breaking – a cataclysm that forever reshaped the world. Saved by her mother’s legendary time-stasis spell, Ali wakes thousands of years into a dark future. Everything she knew and loved is gone, buried under a mountain, transformed into a twisted dungeon by the malevolent will of the Lich. Now, Ali must confront her deepest fears, mastering the arts of battling monsters and braving a town riddled with corruption. As the Lich's grand design shadows her every move, she scrambles to forge new friendships and unearth ancient knowledge in her fight for survival. Why must she struggle? All she had ever wanted was to curl up in a comfy chair with a few thousand good books. But the immortal Lich is drawn to her unique magic, ever hungry for more power to fuel his cold-hearted ambitions. How will she survive the giant target painted on her back as her advancement slowly reveals the horrifying truth of the Class she chose to save herself? Will she falter, forced into the eternal servitude of undeath, or will she rise against all odds and cast him down, ridding the world of his evil?

A legendary powerhouse of his generation, tired of the bustle of the peak, returned to the ordinary city and started a new life as an ordinary teacher. He wrote the legend in the city.

Magnificent mountains and rivers, the rising powerful ones. Some ancient martial art masters stood at the peak, becoming legendary. Some financial crocodiles rose up in the minuscule places, laughing arrogantly.

However, watching the school beauties was better than fighting and killing; educating was better than fighting for fame.

- Description from Novelupdates

Riku Barusak is a hard-working child. Despite possessing an innate superior physical strength and having withstood harsh training she fails to unlock her talent as a spiritualist. The failure results in her being thrown away by her family.

Abandoned, the only ones that extended a hand to her were the demons, the greatest enemies of the human race. Serving under them as a soldier she becomes a weapon of human slaughter, a fiend that should never have existed.