It's Not That Difficult to Slay Demons, Isn't It?

Spend your lifespan to infuse martial arts, and you can perform unlimited deductions. A mere mortal in Xinyi has a lifespan of only a few decades. Fortunately, he can slay demons and gain longevity from the opponent. Are demons just those hideous-looking inhuman creatures? When Xin Yi killed a being who claimed to be an immortal, he looked at the increase in longevity on the system panel and fell into deep thought... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.