The Young Hero's Weapon Shop

As soon as Guan Jiujiu woke up after transmigrating, she discovered that she had a System bound to her: [Hero's Weapon Shop] Young lady, to defeat the Demon King, please open a weapon shop near his palace and help the hero bring him down! Guan Jiujiu looked at the Yue Lai Inn in front of her. What Demon King? This is the Central Plains martial world! The System fell silent for a moment, then quietly crossed out the word "hero": [Young Hero's Weapon Shop] Young lady, to defeat the Demon Cult, please open a weapon shop at the foot of their mountain and help bring down the cult leader! So Guan Jiujiu had no choice but to open shops everywhere, at Xianggan Palace, at Baiqiong Peak, and at... Hey, wait! Why is this final battle happening in my own backyard? Wait, why is the final boss my own senior brother?! Thinking of all the years her senior brother had bullied her, Guan Jiujiu took one second to think, then gleefully started making divine weapons like crazy. All right, you thick-browed, big-eyed bastard. You're finally in my hands! #I'm harvesting chives at the foot of the Demon Cult's mountain #Young hero, the Demon Lord and the Dragon Spring Sword are a perfect match! Guan Jiujiu's little diary: #Did Senior Brother beg for mercy today? No! #Why is Senior Brother even more of a jerk than last time? #You vile dog, Gui Yiyi. We are mortal enemies. #How should I write a wanted notice for the martial world? Got it! [Reward for capturing boss Lu Guiyi: Dragon-Slaying Saber. Guaranteed critical hit!] Lu Guiyi's little diary: #Did Junior Sister realize I like her today? No. #Junior Sister really is even cuter than last time. #Junior Sister won't listen to me anymore. This is so hard. #Lately, Junior Sister has sent so many people to find me, and the prize is still the Dragon-Slaying Saber? Ah, she must miss me so much. I want to write a shameless dog of a male lead, hahaha. The type who's cold and elegant in public, then gets called a bastard by his junior sister the moment he turns around. A bickering couple who can't get enough of each other. Core theme: The most important thing in life is to be happy