Foreign
The twins' sojourn in France had been brief and only at their mothers' demand. The city bored them—although the twins were slightly interested in foreign fashion, they were not interested in foreign girls. Hikaru was particularly moody and upset the entire trip, and despite their strong mental link, Kaoru felt like he was banging his head up against a brick wall every time he tried to speak to his twin.
Being unable to read his twin was not normal for him, and it frustrated Kaoru.
Hikaru, on the other hand, was fiercely upset because the girls were flirting with his Kaoru, touching his Kaoru, giggling at, smiling at, fawning over his Kaoru, and that was not allowed. Any girls that tried to flirt with him were pushed away instantly—and word spreads fast amongst girls, so from then on, any girls that flirted with him had mistaken him for Kaoru. Kaoru was more polite to the girls, at least indulging them with a sweet smile, and every time he did this, Hikaru's blood boiled.
Feeling like this was not normal for him, and it frustrated Hikaru.
These feelings were strange on either side of the mirror.