Where do you belong- the employee working 9-6 or the employee staying overtime? Will you consider yourself efficient?

I am a kind of employee who believes in punctuality and time management.
I would like to work only8 hours per day with proper planning and100% effectiveness.
But my company culture is such that we are forced to work12 hours per day without being paid for overtime, but they dont understand our effectiveness is getting reduced and negative impact on morale.