Neo-Queen Serenity awakened the slumbering Earth in the 30th century, and ruled over it lovingly, residing in Crystal Tokyo. But, what about her King? Would this shining Utopian Kingdom be the same without him? I believe it would be quite the opposite; Crystal Tokyo might not even stand without King Endymion.
As a young man, Mamoru was highly intelligent, and knew a great deal about computers, programming, science and the like. Actually, much like Ami, he was knowledgeable in a wide range of subjects. He used this knowledge to design, create and run the intricate inner-workings and technology that make up Crystal Tokyo in the 30th Century.
Neo-Queen Serenity possesses the power and love to rule over the Earth and protect it. However, she does not have the skills or intellect required to accomplish what her lover does. Just as when they were young, Serenity and Endymion's differences compliment each other to form a cohesive, solid whole. I thought it was very endearing how King Endymion expressed how helpless he felt without Neo-Queen Serenity at his side. It was very obvious how deep their bond still ran, even in the 30th century.
King Endymion is very regal, and just by looking at him I sense a powerful yet gentle essence about him. Mamoru's importance in all of his forms and ages are so often overlooked; in reality he always serves a vital role, and King Endymion is no different.