[Martial Arts] + [Deduction] + [Keeping a Low Profile] + [Decisive and Ruthless]
In an age of chaos ruled by demons, life is as fragile as grass.
Ordinary mortals live no more than sixty years, and can never glimpse the Heavenly Dao.
Demons run rampant, yet enjoy lifespans of tens of thousands of years.
Xu Yin began as an officer in the army. Fortunately, he gained the aid of a martial arts deduction System, allowing him to spend his lifespan to deduce martial arts to their utmost limits.
Spend lifespan:
[Stone-Splitting Fist] deduced into [Mighty Mountain-Leveling Fist], then into [Divine Art: Moving Mountains]
[Light Cloud Step] deduced into [Bluebird Drifting Step], then into [Shrinking the Land to Inches]
[Health-Nurturing Art] deduced into [Greenwood Qi-Nurturing Method], then into [Qi Swallowing Rivers and Mountains]
Ever since awakening the deduction System, his back no longer aches, his legs no longer hurt, he no longer has to work 996 overtime while studying manuals, and he doesn't have to wreck his health or lose his hair training. From then on, Mom never has to worry about my studies again!
However, Xu Yin has developed a serious psychological condition as a result: at all times, he feels intensely insecure about the limited lifespan in his pocket.
If it isn't enough, then take it. No, borrow it!
At a feast of demons, Xu Yin drew a demon-slaying saber forty meters long and glared at the towering demon immortal in the seat of honor, grinning viciously.
“Today, you will lend me your lifespan, whether you want to or not!”
This book is also known as Xu, the Great Demon, in the Eyes of Demons, The Secret Diary of Xu, the Great Demon, Borrow Five Million More Years from Heaven, When Did I Ever Say I'd Pay It Back?, and Since You're Here, How About Another Eight Hundred or a Thousand?
Too lazy to type