You had an average life, living in a world that was fine in Japan, yes there was fights and clans, but you stayed as best you can in your like of work, until...

During the night, you were returning home after training with a friend, they had returned peacefully, so from your perspective, you would be fine... And, you can continue from here.

You may start from the current timeline or from when the Demon Slayer corporatiom was first founded, the path ahead is yours to choose and forge, so do so.