My Ex-Girlfriend is the Strongest Guild Master and I'm the Weakest! - Magic & Battle System

In the tenth year after the new era, the world finally came to an end. Zhang Mu truefully waited for his death, but unexpectedly found that he had returned to ten years ago. With his memory about the future, he swore that he would change the calamitous history, saving the earth from being destroyed! Walking dead, zergs, evolvers, and various mutated animals… nothing can stop him! The first step is to retrieve his identity as an era merchant , then find all the treasures he can remember to enhance himself!

- Description from Novelupdates

After traveling to the Great Wilderness, Shen Can became the Ancestral Temple Keeper of the Blazing Flame Tribe due to his 'frail' body, responsible for the daily cleaning, offering incense, and routine sacrifices at the Clan Ancestral Temple..Shen Can fulfilled his duty as Ancestral Temple Keeper by using the 'Simurgh Blade' to pierce Wild Beasts' necks, extracting their blood to offer to the ancestors, only to discover that he could absorb their lifespan to deduce a cultivation method.

An 18-year-old poor college student tried to apply for a job as a tutor but his life almost ended as demons' meal. In his last breath, a mysterious woman gave him a strange power. When he opened his eyes he had turned into a demon with a system that would turn him into… A pervert.

Now he must lived with his dual identity as a model student named Ethan and an incubus named Damian.

“Will you marry me, Anais?” The male lead proposed to me. “What about Selena?” “Selena doesn’t matter. You’re the only one I’m interested in now.” Even without a hint of interest in the female lead. “I’m sorry, but I…” Before I could even utter my refusal, the refreshing sound of coins rang in my ears. [asdf has donated 100 points!] Accept and get ten thousand points “Shall we go pick out a ring first?” Forget about conscience; if it’s fun, that’s all that matters.