A Mandarin is a high-ranking functionary in a Kuei-jin Court, serving as administrators to the reigning Ancestor. Nominally drawn from jina who have performed admirably at one capacity or another, Mandarins by and large are known for their role as advisers, spiritually or otherwise.
A singular caste within Kuei-jin society, the Mandarins are a taciturn and insular lot who frankly puzzle many young Wan Kuei. That said, many take the time to tutor their juniors on the subject of enlightment, and without their quiet administrative work, many of the Courts would grind to a halt under the weight of bureaucratic inertia. Many also serve as ambassadors to the different courts.
Finally it is their responsibility to choose an Ancestor, which is a very big deal, to say the least.
A Mandarin is a Wan Kuei who has progressed to rank 6 of their respective Dharma, and has decided to take an administative role in their region's Court. This is not necessarily a static role, as many Mandarin have journeyed on field missions on behalf of their courts.
Take note hitting Dharma 6 does not automatically make one a Mandarin, as it assumes the character taking on an the actual administrative position. However a character getting to that point of enlightment may have the necessary talent to become a Mandarin, if a Storyteller chooses.