His brother had asked him once what it felt like to fight with only half of your chakra. Itachi had compared it to reaching a closed door made of glass. You could see what was there on the other side, you could

feel

it, but no matter what you did you could not reach it. And yet it wasn 't nearly as annoying as his brother seemed to think it was. How can you miss something that you 've never had? Sasuke had been lucky enough to meet his soulmate the first year he joined the academy. Itachi, however, had yet to meet his own and therefore had never unlocked the other half of the chakra that should have been available to him. He had never seemed to need it. Having only half of his chakra had not stopped him from becoming the youngest captain ANBU had ever seen.