Ms. Guide is an employee of Kaiba Corporation. She's in charge of helping the kids participating in the Legendary challenge tournament being held in Domino City.
Saikyo Card Battle
She meets Protagonist at the beginning of the Legendary Challenge tournament and teaches him the basics of Dueling. Later, she promises a date to the winner of the tournament making all the Four Heavenly kings, but Tsukiko gets more serious to win it.
After Protagonist wins the tournament and the Phantom rare card she has a "date duel" with him.