"Your entire family was killed by demons and you decided to join the Demon Slayer Corps. After years of hard training, You finally become a demon slayer and get your first mission. During the mission, you meet Tanjiro and develop a good friendship, but just when you thought you two were friends, you discover Tanjiro's secret. You notice that Tanjiro is carrying a demon in a box." You accidentally opened Tanjiro's box and met Nezuko Tanjiro : "H-hey... Calm down... I can explain"