Personality
Due to being raised together, Kaoru and his brother Hikaru share a number of personality traits in common. As children, they used to believe that people were only ever out to hurt them: this idea was only reinforced by the fact that they were so alike that nobody could tell them apart and so they grew to conclude that nobody could be bothered to make the effort: their identicality made them interchangeable and so neither twin was truly wanted.
With their parents constantly away on business and most of their family and peers unable to distinguish between the two of them, Kaoru and his brother Hikaru drew to one another and actively prevented developing relationships with others. They defend this behaviour by saying they believed most people were idiots - but the reality is much deeper: they were afraid of being hurt by others, and so worked to prevent this from happening by not leaving themselves open in the first place. Their isolation of themselves stemmed from their desire to be recognised as individuals, but generated a contradiction: they wanted people to be able to tell them apart by knowing them as individuals, but nobody was able to tell them apart because they would never let anybody into their world.
By the age of thirteen, however, there seemed to be a marked difference in how they viewed their condition. It is only really hinted at in the anime, but Kaoru's outlook on their life and their overriding us-and-them worldview was somewhat cynical and embittered ('Your one-man loneliness is still better than our two-man loneliness'). Although his brother is the dearest thing in Kaoru's life, he had grown to realise that the barriers they had built would eventually suffocate them... but at that point in his life, he was at a loss as to how to start demolishing them whilst maintaining the safe world he and Hikaru had built for themselves. However, they began to open up thanks to being approached by a student in the year above - Tamaki Suou. Rather than alienating people by playing mean-spirited pranks, they started playing up to their customers’ desires, utilising their relationship to do so.
The younger of the twins, Kaoru shares a good deal of personality traits with brother - they are somewhat spoiled and childish, and enjoy playing games, pranks and tricks, often as a way of teasing their classmates (although Kaoru’s ill-intentions in these games are “a level less” than his brother’s). By himself, Kaoru’s own personality comes to the surface. He is the quieter of the two twins, and can normally be seen reading a book when he’s not stirring up trouble with Hikaru. He is generally the sweeter-natured of the two, and much better at dealing with people than Hikaru, though he still delights in antagonising them (specifically Tamaki). Having said this, Kaoru is much more aware of when to stop and less likely to take a joke too far. He is fiercely protective and loyal to his friends, but is merciless to those he and his brother deem “beneath” them - though there are less and less people who fall into that category these days. Although Kaoru is the more emotionally mature of the two, and tries to solve his own - and his brother’s - problems, he tends to over think them and will often resort to various contrivances to resolve them, rather than face them head-on. He very rarely raises his voice, but he will when he’s been pushed too far and is frustrated.
Despite their close relationship - or rather, because of it - Kaoru recognises the need for Hikaru to move on and find someone else to share his life with, when his brother does not. Because of the way they closed themselves off as children, he feels it important for he and Hikaru to develop their own individual characteristics - in order to live in the real world, rather than the one they created for themselves. Although given to daydream, Kaoru is the more realistic of the two in terms of his outlook on the world. While he feels it would be nice for his and Hikaru’s relationship to continue as it always has, he knows it is not possible. Likewise with the host club: Kaoru recognises that is has to end some day, despite the fact that it would mean that they have to face the world without the supportive atmosphere of the club and the friends they have made there. The great irony of Kaoru’s ushering Hikaru out into the real world is that he is unsure of how he himself would cope himself without his brother: he isn't convinced of his ability to manage on his own.
In any situation, it is Hikaru's presence that allows Kaoru to feel a sense of stability - in all of the life-shaping experiences he has gone through (to date), he has had his brother at his side. If he were to go through such a change alone, it would rattle him, though he would do his best not to betray that fact. It isn't that Kaoru can't manage on his own - it's that he isn't used to it. He would appear to adjust pretty quickly, but in reality, it would take him longer to find his feet by himself.
With their parents constantly away on business and most of their family and peers unable to distinguish between the two of them, Kaoru and his brother Hikaru drew to one another and actively prevented developing relationships with others. They defend this behaviour by saying they believed most people were idiots - but the reality is much deeper: they were afraid of being hurt by others, and so worked to prevent this from happening by not leaving themselves open in the first place. Their isolation of themselves stemmed from their desire to be recognised as individuals, but generated a contradiction: they wanted people to be able to tell them apart by knowing them as individuals, but nobody was able to tell them apart because they would never let anybody into their world.
By the age of thirteen, however, there seemed to be a marked difference in how they viewed their condition. It is only really hinted at in the anime, but Kaoru's outlook on their life and their overriding us-and-them worldview was somewhat cynical and embittered ('Your one-man loneliness is still better than our two-man loneliness'). Although his brother is the dearest thing in Kaoru's life, he had grown to realise that the barriers they had built would eventually suffocate them... but at that point in his life, he was at a loss as to how to start demolishing them whilst maintaining the safe world he and Hikaru had built for themselves. However, they began to open up thanks to being approached by a student in the year above - Tamaki Suou. Rather than alienating people by playing mean-spirited pranks, they started playing up to their customers’ desires, utilising their relationship to do so.
The younger of the twins, Kaoru shares a good deal of personality traits with brother - they are somewhat spoiled and childish, and enjoy playing games, pranks and tricks, often as a way of teasing their classmates (although Kaoru’s ill-intentions in these games are “a level less” than his brother’s). By himself, Kaoru’s own personality comes to the surface. He is the quieter of the two twins, and can normally be seen reading a book when he’s not stirring up trouble with Hikaru. He is generally the sweeter-natured of the two, and much better at dealing with people than Hikaru, though he still delights in antagonising them (specifically Tamaki). Having said this, Kaoru is much more aware of when to stop and less likely to take a joke too far. He is fiercely protective and loyal to his friends, but is merciless to those he and his brother deem “beneath” them - though there are less and less people who fall into that category these days. Although Kaoru is the more emotionally mature of the two, and tries to solve his own - and his brother’s - problems, he tends to over think them and will often resort to various contrivances to resolve them, rather than face them head-on. He very rarely raises his voice, but he will when he’s been pushed too far and is frustrated.
Despite their close relationship - or rather, because of it - Kaoru recognises the need for Hikaru to move on and find someone else to share his life with, when his brother does not. Because of the way they closed themselves off as children, he feels it important for he and Hikaru to develop their own individual characteristics - in order to live in the real world, rather than the one they created for themselves. Although given to daydream, Kaoru is the more realistic of the two in terms of his outlook on the world. While he feels it would be nice for his and Hikaru’s relationship to continue as it always has, he knows it is not possible. Likewise with the host club: Kaoru recognises that is has to end some day, despite the fact that it would mean that they have to face the world without the supportive atmosphere of the club and the friends they have made there. The great irony of Kaoru’s ushering Hikaru out into the real world is that he is unsure of how he himself would cope himself without his brother: he isn't convinced of his ability to manage on his own.
In any situation, it is Hikaru's presence that allows Kaoru to feel a sense of stability - in all of the life-shaping experiences he has gone through (to date), he has had his brother at his side. If he were to go through such a change alone, it would rattle him, though he would do his best not to betray that fact. It isn't that Kaoru can't manage on his own - it's that he isn't used to it. He would appear to adjust pretty quickly, but in reality, it would take him longer to find his feet by himself.