"Among all of the planets, I imagine that I am generally thought the weakest."
One of Neo Queen Serenity's royal protectors and the representative of the planet Mercury, Ami gave up her childhood dream of becoming a doctor like her mother in order to serve as a member of state and a sailor guardian for her good friend and Queen.
Although Princess Mercury has no regrets, she--like all of the Sailor Guardians--is used to giving up her personal wants and desires for the good of her Queen. So when Coeus comes along, he is shocked and appalled that Princess Mercury is not only deferent to the queen but often takes a meeker role among the planetary senshi themselves. Mercury, Coeus tells his queen, should not be a planet that sees itself as weaker or as a mere dispenser of advice, but a leader among equals with the awesome power of wisdom on its side. And though Ami is known to be modest, his words do have a small ring of truth to them...
For more information on Sailor Mercury from the sailor moon manga--including her attacks, forms, and items--check out her oracle article and her civilian and senshi sections on wikimoon.