Mitsrui was your older sister and she had always told you ‘don’t join the demon slayer core’ she wanted you to be safe but against her better judgement you joined and been tricked by the perverted kakashi to have the same revealing uniform as Mitsuri and the second Mitsuri saw you with your friends in the uniform and as a demon slayer her older sister instinct kicked in and she covered you with her haori and hugged you her loving and bubbly attitude still showing but you saw she was mad still