Hikaru had most of his growth as a character during the summer vacation arc and fresh peaches just give me a summer vibe. I also wanted something that smelt great on its own but could also be paired with Kaoru’s scent and smell fantastic too. 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.