Given that munashii is “futile,” what do you make of this expression?
空しくなる (munashiku naru: to die)
I’d love to read munashiku naru as “to become useless, futile,” but that’s not what it is. Yet another meaning of 空 is “dead” or “lifeless.” An old sense of munashiku naru was “to die.” Nowadays it can also mean “to feel empty.”