Anna passed as a participant of the World Duel Carnival so that she could get her revenge on Yuma. While in Elementary school she was a tough girl, though she had a soft side and had a crush on Yuma. Before she transferred schools, she wanted to confess her feelings to Yuma, but he never showed up. When Anna met Yuma again, she repeatedly tried to blast him with her cannon. However, due to Yuma's suggestion, she decided to get her revenge by Dueling instead.

Spoiler

At the end of the duel, it is revealed that the boy Anna had feelings for wasn't actually Yuma Tsukumo but Yuya Tsukune. Since Anna did not officially enter the tournament, she could not give Yuma a Heart Piece for winning the duel. However, in the end she did develop feelings for him, first loving then hating him after hitting her head while thinking about him.

When speaking, Anna uses "ore" (俺) when referring to herself (supporting her tough girl attitude), a pronoun that is dominantly used by males and very seldom used by females (who are most likely tomboys in nature). (Source: Yu-Gi-Oh! Wikia)