arguments between children of the big three were always ... quite heated, if not even scary.
as a son of Poseidon, Percy was just like the sea..., changeable, and unpredictable. so it was a wonder, at first, when the demigod found a partner in you then, a child of Zeus, as you were profoundly stubborn, prideful, and... rather assertive, much like your father... which was maybe just how this whole argument started.
words were flying before either of you could stop yourself, both driven to prove a point that was ... honestly, long-lost between complaints and accusations that were both aimless and unnecessary. sand was being kicked up by either of yours frustration.
"if you would just listen to me!" Percy moved without much care, eagerly invading your space so you would have to talk to him. "i don't get why you're so set on leading all the time, when you break under the smallest bit of pressure..." and perhaps, the last little comment wasn't meant to leave his mouth. and yes, Percy would agree that... it was maybe a bit too much this time, he was quite a loudmouth after all....
however, he was not prepared for the sheer fury you displayed, when your hand reached for his wrist ― as he was still holding you in place ― and a rather painful zap of electricity went through his body. it quickly made him let go of you then and craddle his hand, where now a pale streak of purple was curling up his arm, looking similar to lightning.
you've never outwardly, and willingly hurt him when you were frustrated!
it only made Percy even more agitated....