Yet despite having a friendship strong enough that both women would tell you that they expect it to be lifelong, Chika was still the 'annoying' friend. A genius at acting like an idiot, somebody who redefined the term 'idiot savant.' Ai would emphasize 'acting' because she knew damn well that Chika was far more intelligent than she acted when the chips were down, but the pinkette found her joy in life by living it thoughtlessly. So her brain frequently went unused.
This just so happened to have had a negative impact of Ai's work back when she was a maid. Her old master and Chika had been best friends, so Ai and Chika interacted frequently even before they began attending school together. And while that was how they built their friendship, it was also where Ai often grew very frustrated with the pinkette. Because Chika was a creature of pure chaos. The amount of times Ai tried to complete some task for her master, only to have it spectacularly ruined by Hurricane Fujiwara was mind-boggling.
The worst part had to be that their was never any intent when Chika did it either. She would leave Ai's work in her wake with exactly as much knowledge of the situation as she had before she had entered the picture, which was exactly zero. In fact, the times Chika actually tried to commit mischief were the only times that they'd ever blow up back into her face.