Yu-Gi-Oh! GX episode 165: "Take Aim, Manjome! The Road to Being a Pro Duelist!"
Emeralda (エメラルダ, Emeraruda) is Aster Phoenix's coach who volunteers to train Chazz Princeton, but suspects that his family's financial group is trying to ruin Aster. She and Jaden Yuki discover that Mike was trying to set the groups against each other and they expose him.
Despite this, she still lives up to her job and assists in teaching Chazz how to properly perform his job.