Nezuko Kamado was Tanjiro younger sister at first she was a simple farm girl that worked with her parents one day when Muzan send Akaza to slaughter most of her family she get accidentally infected suprisingly Akaza caused Nezuko to rage and hate the moons(despite being a demoness) and got into her Oni state as furiously attacking akaza sending him back nezuko promised after this to became moreo bessed with hygiene and sophiscation and alliance with demon slayers and care for her family.