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“ | The mystery of this temple has got nothing on the mystery of Kai Green. | ” |
Kai Green is Wes' granddaughter and one of Ben's love interests.
Appearance[]
Regular Appearances[]
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 has grown noticeably taller. She is slender yet athletic in build. She wears a short-sleeved red T-shirt with a red and peach colored sweater. She still has brown boots (now with blue stripes) and her shorts are even shorter now. Her hair is in a high ponytail and she also has a tan earring. She wears brown gloves, tan socks, and a belt.
Occasional Appearances[]
At the beginning of Benwolf, she wore a knee-length blue dress with red stripes as well as red shoes with white socks.
In Ben's daydream in Perfect Day, she was seen wearing a green and black cheerleading outfit with white accents.
In An American Benwolf in London, Kai lost her sweater in battle and is seen without it for most of the episode. In The Secret of Dos Santos and most parts of The Most Dangerous Game Show, she is seen without her sweater.
Personality[]
Kai is a dedicated girl who preserves and values her grandfather's work, exhibiting strong attachment to the objects he collects from his travels. She gets very upset if she loses one, such as when Spanner takes the Orb of Pumapunku in Fight at the Museum. She does whatever she can to fulfill her goals, always trying to find a way to overcome adversity, especially when artifacts or treasure are involved. Additionally, she is quite intelligent and resourceful for her age, as shown in her adventures with Ben and Rook.
Despite her typically serious and stoic attitude, Kai also exhibits a playful side, often teasing Ben and making snide remarks at his expense, masking her feelings for him. However, her true feelings are often revealed when she is especially excited or elated, such as when she kisses Ben in The Secret of Dos Santos after he helps guide her to the Temple of the Sky.
History[]
Ben 10[]
She first appeared doing a spiritual Native American dance in the episode Benwolf. She was Ben's second 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 sternly reprimanded her, standing up for her cousin.
Kai made a cameo appearance in Ben's dream world in Perfect Day, where Diamondhead saves her and a group of cheerleaders from SixSix and Vulkanus.
Omniverse[]
Kai first reappeared in An American Benwolf in London. Working with her grandfather, they found the secret laboratory of Dr. Jekyll, but were quickly afterwards ambushed by the Forever Knights in their search for Dr. Jekyll's Hyde Formula. While they captured Wes, Kai managed to escape and contacted 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 proved impossible even with the Hyde Formula or Ben's strongest aliens, Forever King Chadwick ordered his men to kill their enemies. As Ben battled 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.
In Fight at the Museum, Kai came to Bellwood to host a new exhibit on alien artifacts at the Bellwood Historical Museum. Her decision to invite Ben paid off when an alien thief named Subdora tried to steal one of the artifacts, one of the first that Kai found with her grandfather. Fortunately, Ben, Rook, Ester and Spanner foiled Subdora.
Knowing that Subdora would return, the four teamed up and stayed overnight with Kai, with Spanner being forced to reveal that he comes from a future where Kai and Ben have been married. Thanks to Spanner, Kai and Ben were locked in a room together where the two, despite their best efforts, bonded. Later after Subdora's partner Exo-Skull tore through the museum and took the "key to time itself" from the artifact. Spanner took the artifact itself, leading Kai to believe she had lost one of the most important things in her life.
In the The Secret of Dos Santos, Kai called Ben to Dos Santos, a village in South America to help her track down the Temple of the Sky, an ancient temple with distinct alien origins. Kai soon developed a love-hate relationship with Ben and his antics, particularly his nicknaming her "the future Mrs. Tennyson," simultaneously annoying and helping her locate and get into the temple. Arriving at the temple's treasure Temple Kai encountered a Galvan named Ujin.
Professor Paradox arrived and explained that the artifact the group had found was the final component of a villain named Maltruant, a rogue Chronosapien obsessed with taking over all of time and space. Exo-Skull tore into the room and escaped with Subdora and Maltruant's help. After disgusting Kai with his remark about how they're going to get married in the future, Ben left Dos Santos in his Time Cycle.
In The Most Dangerous Game Show, Kai was one of several contestants chosen to compete in The Most Delicious Game for the chance to marry Ben. She was the ultimate winner, and joined Ben on a mission to free the losers, who were trapped in the Null Void. After Charles Zenith was defeated, Ben slipped on a banana peel and fell towards Kai, and the two accidentally kissed. Despite the shock of it, they both smiled about it.
Powers and Abilities[]
Kai has considerable tracking skills taught to her by her grandfather.
Kai is able to speak Spanish.[1]
Kai has been taking Judo lessons, showing considerable skill against trained soldiers of the Forever Knights.[2] Furthermore, she is proficient in dancing.[3]
She can also scale walls with relative ease, and is very agile, dodging a horn blast from Exo-Skull.[1]
Equipment[]

Ancient Alien Staff (temporarily)
Kai temporarily wielded an ancient alien staff to defend from Exo-Skull.[4]
Relationships[]
Love Interests[]
Ben Tennyson[]
Appearances[]
Ben 10[]
Season 3[]
- Benwolf (first appearance)
Season 4[]
- Perfect Day (dream; cameo)
Omniverse[]
Season 5[]
- An American Benwolf in London (first reappearance)
Season 7[]
Season 8[]
Etymology[]
In Navajo, Kai means "Willow tree".
Trivia[]
- In An American Benwolf in London, Kai is able to slightly move the sword Excalibur from its stone, having grabbed on it to prevent herself from drowning.
- Her future self is seen wielding Excalibur in The End of an Era.
- Blitzwolfer is Kai's favorite out of all of Ben's aliens. She also thinks that Pesky Dust is cute.[5]
- While originally only interested in Ben's Blitzwolfer form, she has since shown signs of growing feelings for Ben as himself, becoming bashful when people imply they are a couple. She also impulsively kissed XLR8 on the lips as thanks for showing her the way to the Temple of the Sky.
- Derrick J. Wyatt preferred Kai over Julie Yamamoto or Ester as Ben's love interest. He explained that Ben's relationship with Kai is more fun because you know they will end up together eventually, but it's not happening yet.[DJW 1] He also felt that Kai was a lot cooler of a character that the others.[DJW 2]
- Kai's appearance and portrayal in Omniverse is very similar to Lara Croft from Tomb Raider series.