I Became the Tyrant of a Defense Game - Chapter 760

The number one swordsman Zhao Jiangui is the martial world’s best hope for peace: All he has to do is seduce the Demon Sect Leader.

The Special Investigations Unit is a covert organisation that no-one in the city knows about, dedicated to investigating bizarre occurrences beyond the comprehension of the living. The Chief Zhao Yunlan isn’t a simple guy either, being the inheritor of the Guardian Order, he has always been a righteous conformist, excelling between realms of the living and the dead. While investigating a school suicide case, Zhao is attracted to the calm and reserved Professor Shen Wei, but the Professor seems to be rather fickle towards him…

- Description from Novelupdates

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?

Our protagonist Caam is a man from Earth that was reincarnated into this world as a demon. In order to survive, he spared no effort in avoiding the sparks of battle and without noticing it, he became strong himself.