Even with the appearance of a cat with a crescent moon bald spot, Luna is Usagi's mentor. Her job is to help Usagi become the best Sailor Guardian she can be. She is mature, but not above jesting as Usagi. She's very serious about her mission and will see to it that she accomplishes it.

Please don't try to give her a high pitched cat cartoony voice. I'd like her to sound mature.