I recommend " My Sister Has No Opponent Ahead ". This is a light novel, a derivative doujinshi novel. The main character had a mutated system called the 'Slaying Knife Forging System.' The Slaying Knife he forged was customized for his younger sisters and was even named after them. For example, the Great Red Lotus Ice Wheel Pill, the strongest ice-type weapon, and the Flowing Blade-like Fire, the strongest fire-type weapon, etc. I hope you like my recommendation.😗