Identical twins Hikaru and Kaoru entertain girls at the Host Club with their game of many years - "Which One Is Hikaru." Haruhi finds this very droll since she can distinguish the twins quite well, which she demonstrates. This is, in fact, remarkable, something no one else has ever been able to do it. When she explains how Hikaru is the more mischievous of the two, the twins react differently, dismantling their longstanding united front against the world to turn against each other in furious and violent squabbling.
—statmanjeff