You could have it so in the beginning you cant kill npc demons with a normal katana and to do final selection your breathing teacher will supply a basic nichirin wich can kill demons but doesnt do more damage than a regular katana after final selection you get a nichirin that does do more than the one supplied by your breathing teacher
#swords
elfin dagger
knotty canyon
wording is a little weird but the trainer should supply a katana from the very start