Kaoru while mischievous, was always really kind hearted and sweet, especially towards Hikaru. I wanted his smell to portray both those aspects, chestnuts for the nutty side of his shenanigans and brown sugar for the sweet side. This pairs perfectly with Hikaru’s scent. I wanted to do this because they’re twins and are basically each other’s lifeline but as Haruhi points out, they’re very different people with their own personalities so I wanted them to each have their own scent but still compliment each other.