Jo Diamonds, also known as Joe Diamond XVII or Jo King Diamonds XVII, is a central character from the 1997 original video animation Wild Cardz, which is also known as Jaja-uma Quartet. She is a member of a group of heroes known as the Crown Knights, who are dedicated to protecting the Card Kingdom from invaders and other threats. Jo is characterized by her youthful, adolescent appearance, with distinctive long red hair that reaches past her hips and green eyes, identifying her as a teenage female protagonist within the action-comedy fantasy setting.

In the narrative of Wild Cardz, Jo Diamonds acts as the primary powerhouse of the Crown Knights, frequently engaging in direct combat against the series antagonists, which include massive war machines shaped like chess pieces. Her primary role in the story is to use her incredible physical abilities to defend the Card Kingdom, often alongside her fellow knights. The group's dynamics involve Sunday Spades as their stoic leader, while Jo acts as a key fighter. Other members include Casa Clubs, who has heightened senses, and Coco Hearts, a user of psycho-magic. While the series emphasizes action over extensive individual backstory, Jo is defined by her heroic and proactive nature in the face of danger.

The most defining aspect of Jo Diamonds is her exceptional speed. She possesses supersonic speed and the ability to fly, making her an incredibly agile and fast-moving combatant. Her signature power is known as Diamond Magic, which is described as making her almost invincible in battle, allowing her to reach and even surpass light speed. This formidable combination of superspeed, flight, and magical resilience forms the core of her abilities, enabling her to confront powerful enemies. As the seventeenth iteration of Joe Diamond, her name carries a legacy, though the specifics of this lineage are not deeply explored within the OVA episodes themselves.