During their date, Hikaru runs off due to another encounter with Arai, and a thunderstorm occurs. Worried about Haruhi, Tamaki calls Hikaru, accuses him of selfishness, and tells him that Haruhi is afraid of thunder, accidentally revealing Haruhi's weakness
Since identical twin share the same DNA it’s very likely of them to have same genetic and personality traits. Identical genes are often found in identical twins than fraternal twins as they usually possess different personalities.
