|Age|| 10 (Original Series)|
|Powers and Abilities|
|Abilities||Hand-to-hand fighting skills|
|Relatives||Wes Green (grandfather)|
|Alias||Little Archaeologist (Ester)|
|Alternate Counterparts||Kai Green (Ben 10,000 Timeline)|
|Voice Actor||Bettina Bush|
In the original series, Kai had long, black hair and brown eyes. She wore a red shirt, green shorts, brown boots with white socks. She had silver bracelets and a blue ring.
In Omniverse, Kai wears a long sleeved red shirt with a red and peach colored sweater. She still has brown boots (with blue stripes) and her shorts are even shorter now. Her hair is in ponytail now and she also has a tan earring. She wears brown gloves, tan socks and a belt.
Powers and Abilities
Kai has considerable tracking skills taught to her by her grandfather. In Omniverse, it is revealed that she has been taking Judo lessons, showing considerable skill against trained soldiers of the Forever Knights.
She first appeared doing a spiritual Native American dance in the episode Benwolf. She was Ben's first crush, but she only took interest in him after he started becoming Blitzwolfer because she wanted to, as quoted, "train and tame him". When she admitted to this, Gwen gave her a stern talking to.
Kai appeared in An American Benwolf in London. Working with her grandfather, they find the secret laboratory of Dr. Jekyll, quickly afterwards ambushed by the Forever Knights in their search for Dr. Jekyll's Hyde Formula. While capturing Wes, Kai manages to escape and contacts Ben and his partner Rook for help. Ultimately, they discovered the hidden location of the legendary Excalibur. When removing the blade from its stone seemingly proves impossible even with the Hyde Formula or Ben's strongest aliens, Forever King Chadwick orders his men to kill their enemies. As Ben battles the mutated Forever King, the cave's underground pipes were ruptured and caused a flooding. Convincing the Forever Knights to work together, everyone was able to escape alive.
Ben 10: Omniverse
- In Hawaiian "Kai" means "Ocean" or "Sea".
- In Maori "Kai" means "Food".
- In Portuguese "Kai" is pronounced "cai" which means "Falls".
- In Japanese "Kai" means "King". It can also mean "Sea" or "Ocean".
- In Tamil (one of the Indian languages) "Kai" means "vegetables".
- In Ken 10 it is seen that Kenny's skin color is a mix of white and Native American. According to the pop-up version, Ben would eventually marry Kai in a possible future, and she is Ken's mother.
- In An American Benwolf in London Kai is shown to be the only one able to move the sword Excalibur from it's stone, having grabbed onto it in order to prevent drowning it moved slightly.
- While still greatly liking Blitzwolfer, she has shown signs of growing feelings for Ben as himself, becoming bashful when people imply they are a couple and giving Ben a kiss on the cheek as he leaves.
- Kai considers Blitzwolfer to be her favorite out of all of Ben's aliens.