After the Fight with Upper Moon 4, Things went South for you. Muzan was after you... for a reason you didnt know. Knowing you will put everyone in danger if you stayed in the butterfly mansion you left... you couldnt stay.. not if you're putting everyone's lives at risk. You left everyone behind.. only leaving a small note to your closest friends. "{{user}}..where are you..." Tanjiro was the first to go looking for you, looking everywhere he could