solemn roost
So in the real world every sword needs this thing called edge alignment and if this edge alignment isn't on point your sword would break from wear and tear.
So I was thinking what if you made it if you spammed M1 and M2 you would lose edge alignment and if you deplete this bar so much your sword will break making your sword only do a fraction of damage that you used to (btw when you deplete your bar once you'll be stunned for a second).
You could also make it so different nichirins have different breaking debuffs (like if you have sound one of the blades will actually fall to pieces and you can't use move like string performance).
You also can't do missions in the time your sword is broken.
Then if it breaks you'll have to be escorted to the swordsmith village where you go up to a swordsmith and ask them to fix it it would also cost 500 yen and a scolding of your swordsmith (but if you don't have the yen they'll give you a one off and after that you'll have to do basic quests that don't involve combat).
weary palm
gloomy glade
calm nimbus