Master: Master Shen
Thread Link: dragonballnewhorizon.boards.net/thread/123/operation-kidnapped-figure-earth-quest (Second post for a foreshadow and the final post for gaining full knowledge)
Reason why they'd train you:

For a brief overview of how Kyanite knew about Master Shen: Kyanite learns about the Crane School from the Kidnapped Figure quest. She encounters two formidable men who wore the uniforms from the school as they were part of kidnapping the king of Earth, and later confirmed by the king of Earth of their affiliation of the Crane School. Kyanite, with the permission from the king, decides to visit the school and interrogate Master Shen about the men she fought and whether or not he had a role in assisting the kidnapping of the king.

Aforementioned that the two men she fought were considered to be a few of his top students, when he hears about Kyanite being able to take the two men down, he takes interest in her power and challenges her to a duel to test just how powerful she is since she can't be sensed. She could be considered to be a one of Shen's most powerful students yet when they spar.

Personality wise, these two hold similar traits to one another; they both can be sadistic, unforgiving, and cutthroat when it comes to getting what they want. I can see them trying to one up each other and butt heads at each other. I think they'd have an interesting dynamic as student and master, especially since Kyanite can be a little rebellious against authority besides the CEO of the Red Ribbon Army; but even then, she may talk back.