As children, the twins had a maid they adored but who was, in reality, a thief. They tell her that if she can tell who is who between them, they'll give her the combination to the safe kept hidden in their piggy bank. Unable to tell them apart, the maid breaks open the piggy bank after they fall asleep and robs the family. As she descends from the upper stories of the mansion, the twins wake up and go to her, asking why she broke her promise. She says that she can't tell them apart and, perhaps, no one ever will. This begins their dysfunctional view of others being untrustworthy unless they can tell the twins apart. When they meet Tamaki in middle school, he asks them to join the Host Club and they agree, provided Tamaki can tell who is who, giving him a month to do so. Over time, they grow bored and tell Tamaki to get lost, going back to being mean and selfish, playing tricks on girls who like them and isolating themselves from others. Tamaki, despite being dismissed, is determined and finally figures out which twin is which. They dislike his reason of "intuition," but Tamaki helps Hikaru and Kaoru understand that it's okay to be who they are, but if they remain isolated, they'll never meet the person who can really tell them apart. The twins decide to be a part of the Host Club and enter, as usual, together.