In Season 4 of Ninjago, the ninja find themselves in the midst of a high-stakes tournament of elements on Chen's Island. As they navigate their way through the competition, they come across a young man named Kairo, who is revealed to be the son of the Overlord.
At first, the ninja are wary of Kairo, as his dark elemental powers and ominous appearance make them think he is evil like his father. However, as they get to know him better, they realize that he is not hostile or evil at all.
Kairo is a skilled fighter, and his elemental powers prove to be a valuable asset to the ninja as they make their way through the tournament. Despite their initial suspicions, they begin to trust Kairo and work together as a team to overcome the challenges they face.
As the tournament progresses, Kairo reveals that he does not share his father's desire for power and control. He is kind-hearted and wants to use his abilities to help others, just like the ninja do.
Together, the ninja and Kairo form an unlikely alliance and work together to uncover a plot by Chen and the Anacondrai cult to take over Ninjago City. With Kairo's help, they are able to thwart the plot and save the city from destruction.
In the end, the ninja realize that appearances can be deceiving, and that even those with dark powers can be good at heart. Kairo becomes a trusted ally and friend to the ninja, proving that sometimes, the greatest allies can come from the most unexpected places.