Hikaru and Kaoru Hitachiin seem to share a strong bond that cannot be found in many sibling relationships. That's caused by the fact, that they had grown up together and did everything with each other before confronting the host club. Or as they had stated, they were leaving in a world where it was just them.Although they are considered mischievous, they have their differences: Kaoru is more agreeable, more mature, and considerate of others, while Hikaru is more immature though he is the older 