Board Thread:Episode Discussion/@comment-24573226-20171012080158/@comment-26397825-20171014190535

But...it’s useless. You need aura to use your semblance as a general rule, but aura stops you from being cut or having your bones broken, which makes an “impervious” semblance redundant. If you run out of aura you can’t use your semblance, which means he would be able to be hurt because he has no aura or semblance to use.