Akito didn't know when it started. However, before he knew it, his gaze constantly followed her. Before Akito knew it, he was searching for her wherever she went. He sought her our wherever. Even long before they became close with one another, he was always watching her. Maybe it's because he realized Setsura differs from the other girls; it was one of the things he had first noticed about her.
Most girls he knew are loud, obnoxious, and chatty. However, Setsura differed from them. She wasn't shy or meek. Well, she was quiet when she first came. But, that was only due to her loss of memory. Akito understood that she isn't like that. He has yet to learn about the real her. But even after he learned about the real her. His opinion didn't change whatsoever. Why would it? He had already fallen in love with her.