'Kisai no miya' and 'Chugu' were both empresses and one was not superior to the other but in most cases, 'Chugu" was substantially in the position of the emperor's legal wife.
「皇后宮」も「中宮」もともに皇后であり、互いに優劣はないが、「中宮」のほうが実質的に天皇の正妻としての地位を占めている例が多い。