Kaoru and Hikaru are both wealthy and playful; however, Kaoru is the calmer and more mature of the two. When apart from his elder brother, Kaoru becomes a pleasant person, acting in a selfless and serious manner; but when he is with his elder twin, he reverts to being a scamp-like individual. Although the twins have spent the majority of their lives interacting only with one another, Kaoru demonstrates an understanding about social interactions and innate self-control.
Kaoru is said to be 10% less evil than Hikaru.