EXTRA:The yandere Villainess Is Obsessed With Her Special Servant - Chapter 12: Beyond Service: Teaching the Villainess

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.

Lyle Walt is a young noble boy and heir looking forward to the day he can inherit his family’s territory. Except around when he was 10 year old, his parents started neglecting him more and more in favour of his little sister, Celes.
On his fifteenth birthday, he is challenged to a duel by his sister to see who will inherit the household and horribly loses, being cast out of his family. Afterwards, he gets treated by the family groundskeepers and receives the family heirloom Gem from him that Lyle’s grandfather had entrusted to him. From there, he begins an aimless journey with his childhood friend and former fiancée, Novem, and the Gem-turned-Jewel that houses the memories, personalities, and Skills of seven of his ancestors.

After transmigrating into a SF (Science Fiction) novel and enduring cruel hardships, I ascended to the throne as the Emperor of the Galactic Empire.[Welcome to the Integrated Dimensional Community.]As the community’s Lone SF Transmigrator, I unleashed the poison of new cultures on the uncivilized primitives of the Otherworlds.-Let there be light. To judge the horde of evil, the Apostle of the Goddess sent down a Graviton Surge. Thus, in that place was light along with a massive explosion…-The Grand Duke of the North has shown great interest in your Heattech…-I, as a Namgung, am thankful for the grace akin to the vast sea provided by the Great Hero. By virtue of the Vibroblade bestowed by the Great Hero, the nefarious Demonic Cult has…It seems like these Otherworlders can’t get their sh*t together.

Over a million years ago, the first human contracted with the first Spirit. Ever since then, Spirit use has become commonplace. Humans used Spirits to carry items and start fires. Eventually, even start wars. Thousands upon thousands of years past and one day, one human did the impossible. He transcended his mortality and ascended to the realm above.