[First Part]
[As you as you enter the field when the class is taking place you may notice the strange shift in the air. No one else is around. Are you early? Late? Wasn't it lighter just a few minutes ago?
But more importantly what is this sense of being watched. The leaves of the trees at the outskirts barely rustle. Is someone there?
No, someone is behind you. Someone who wants you dead. Will you dodge their blade in time?]
{OOC: Each person has fifteen minutes to survive or get out of the genjutsu. This basic illusion disrupts energy patterns in the brain. You can get out of it by killing the opponent, causing a minor injury to yourself/using real pain, or correcting your energy pattern through sharing/borrowing energy from someone else. No one is any real danger as all wounds are in their own minds and should they be "seriously injured" the genjutsu will cease immediately.
Others will see the person who is experiencing the genjutsu and being frozen in place/unmoving. Feel free to handwave this part for the rest of the class time or even skip to post genjutsu reactions. The illusion-opponent is a moderate/experienced fighter, but NOT unbeatable.}