Cha Chi is a skilled martial artist from China who utilizes her family's distinctive fighting style. Eight years before the main events, she encountered Kujira Etorofu, who was then living under the pretense of being a boy. Cha Chi issued a challenge, resulting in a promise that if she defeated Kujira, Kujira would become her groom. This agreement fuels her relentless pursuit.

Despite Kujira later realizing and stating her female identity, Cha Chi remains unaware or unconvinced. She persistently vows to make Kujira her husband and views others close to Kujira—especially Sakura Nankyoku—as romantic rivals. This leads to confrontations, including instances where she nearly fights Sakura after misinterpreting Kujira's protective actions toward her.

In combat, Cha Chi specializes in rapid spinning kicks and other techniques rooted in her martial arts, capable of causing significant damage like tearing through walls. Kujira defeats her in a key rematch using the "Etorofu Whale Punch," which overpowers Cha Chi and tears her clothing. After this loss, she formally admits defeat but reaffirms her commitment to eventually win Kujira over. She later transfers into Kujira and Sakura's class, maintaining her rivalry with Sakura and continuing to misinterpret Kujira's intentions. Her speech often ends sentences with "~chi." She reacts strongly to perceived threats to her goal, such as when Kujira shields Sakura from her attacks.