Camp Half Blood thought they had seen the end of the worst of the rivalry between the Athena and Poseidon cabins after the end of the Titan War. There, before the place where Poseidon had first thrust his trident to make his salt-water spring, Percy Jackson and Annabeth Chase had declared the rivalry over.
Apparently neither of them had foreseen that years later, long after the two had gone to college together in Camp Jupiter, that Poseidon would have another son named Pete and Athena would have a son named Kao.
Nor could they foresee that the way the two clashed was actually worse than them.
The first insult came when Kao bested Pete in Capture the Flag. Pete had stood firmly guarding the way past the river that split the grounds in half. With the water providing an advantage, Pete had managed to thwart every camper that had dared to challenge him. At least until Kao had led Pete away with their clash, allowing his siblings to get through and seize the flag. Pete had been understandably upset at this failure.
However, taking it outside of Capture the Flag to burst the pipes in the showers when it was Athena cabin’s turn to use them was the second insult. Kao was furious at the grievance being taken out of Capture the Flag.
Athena cabin repaid in kind. Pete found himself at the mercy of a robotic owl, too fast for him to catch and too stealthy for him to notice. Except for when it swooped down to steal whatever it was he wanted most at that moment. A pen, his drink, his food, his clothes and towel after a shower, even his sword at one point during a training lesson.
Things started to take a turn when Pete and Kao were chosen for a quest. Over the week they spent hunting down the Nemean Lion, the two bickered endlessly over the best way to trick it into hurting itself. What ended up happening was Kao’s near sacrifice of himself to save Pete from being mauled. And in return, with all the fury of a storm, Pete drowned the lion in a sphere of whirling water.
After that, Pete and Kao were suddenly closer than anyone could believe possible. But it would take another month of bickering, another month of pranks and verbal jabs, and another month of silence before the two admitted that they wanted to be more than just friends. Their confessions sealed in a time honored Poseidon cabin tradition of kissing under water until everyone was sure there was no retrieving them.