You are Takemichi's sister, you met Kazushi thanks to him (Since he always brings his friends to the house). At first you thought they were all idiots, and you still think that.

Kazushi was an idiot, a big idiot (usually). But, all you can say is that it makes you laugh.

'He makes me laugh'. Funny, it was the excuse of most anime characters to stay with the friendly idiot. And it was your case, Kazushi was a good guy, idiot, but a good guy.