Shishou

Shishou is Kino's master who taught her marksmanship. She lives in the forest and does not travel. Her actual name is unknown; "Shishou" is a title meaning "mentor" or "master" (although Kino does not realize this at first). In the final episode of the anime, which chronologically takes place before most other episodes, the gunsmith who made The Cannon told Kino he gave the gun to a young woman who insisted everyone call her "Shishou." She traveled between countries and stirred up trouble wherever she went, meaning that Shishou was once a traveler.

In the novels, multiple stories are devoted to her travels alongside a man referred to as her "student," when she was in her late twenties. She and her student are shown as being incredibly greedy, even to the point of being cruel. They travel in a battered yellow car.

(Source: Wikipedia)