"It is not the opposite of Ninjutsu you fool," Ieyasu sighed. "Training with Ryu I'm sure he's covered the elements of Yin-Yang manipulation to you. Yin is the spirit half while Yang is the physical half. This is what creates ninjutsu. If Yin is the epitome of genjutsu how is it the opposite?
If anything it is one half the spectrum as it dwells only with the mind. That being said, your scope of genjutsu is surprising and annoyingly narrow. Genjutsu spans beyond the realm of just the five senses. You said it yourself, it has gained the title of Yin-release in some regards, yin representing the entire spirit or the mind. The five senses are under one's control when we talk about genjutsu, however there are other affects such as hypnosis that exist in the realm of genjutsu. As an Uchiha you should know about the hypnotic eye of the Sharingan. Genjutsu can bend another to your will if the caster so wished. Our ocular powers are a prime example of this. Do you understand?"