Demon Slayer: in Order to Survive, I Will Go Crazy and Become Miserable

[Demon Slayer: Kimetsu no Yaiba] [Spartan Education] [Brother Control Training] [Beat without Disaster] [System] After traveling through time and being Usanya Shikihiko, the beginning is on hell difficulty. The twin brother is named Tsuji Mukai, and there is a future god of death named Tsukikuni Enichi who is on his way. Fortunately, [the most powerful tutoring system] has arrived! As long as you torture... Oh no, educate your younger brother, you can become stronger! Bite! Forced to squat a thousand times under the scorching sun, reward: Sun Iron Prosthetic Leg (with built-in sunlight attribute)] [Ding! Beat up the disobedient Wumei, reward: Perfect Biological Cell x1] [Ding! Let Wu Mei learn calculus and Capital, and the reward will be: Clues to the blue Hibiscus flower] Thus, the most terrifying legend of the Heian era was born. Wu Kuan cried and shouted: "Brother, I really can't eat anymore, this wisteria tea is too bitter!" Yueyan (sneered): "Drink it. This is to make you immune to toxins. My brother is doing this for your own good." Hundreds of years later, Ji Guoyuan drew his sword, only to find Wuhan covered in high-tech armor and holding a heavy firearm. Wuhan: "Did you see the equipment my brother gave me? Breath of the Sun? Times have changed!" The system panel flashed wildly: [The host cultivates the ultimate creature, lifespan +9999!