I havent thought about how you would break a nichirin possibly through something to do with being early on in your slayer journey and not having great sword wielding skills, which is how tanjiro broke his blade twice therefore, as you sharpen your skills your less likely to break it (obviously i dont mean breaking your nichirin every few fights i mean more spaced out incidents like breaking it 1-3 times in total through your playthrough of the game). But when you do break it you may have to deal with an angry blacksmith or something cool like that. and if you want to make changes to your blade if customization is a thing, then you will take a trip to the village which is where you will customise it. Maybe even have the fighting doll as a challenging fight which rewards you with one of the blades it wields which you can get reforged into a functioning sword.
#Swordsmith village.
tall wren
opal hemlock
we've had these suggestions before, please review other suggestions before making your own