He didn't realize he probably doesn't have feelings for her, he pondered whether his feelings were just based on her looks, or if he truly liked everything about her. He was getting ready to tell her he liked her, but he stopped because he wasn't sure of the basis for his feelings. But then they kissed, and his feelings were reaffirmed, hence his "I will follow you everywhere" bit.

EDIT: David, you're fast. But, your post made me think about what you said (regarding his thoughts about sex). I guess an argument could be made that his realization of "like her just for her looks" relates to his wanting to have sex with her, thus mimicking the feelings of wanting to be with her, but I didn't delve at it that far.

His realization that Yamada seems like she wants to have sex (cause he still doesn't know that's all she wants) was much later in the episode, and he was going to act based off that, until the camera people ruined the mood for them.