After school during a class meeting, a male student accidentally gets an erection without realizing it, and the girls in the class notice. This incident triggers a chaotic "erection epidemic" within the class. Students begin conducting various experiments and heated discussions trying to figure out what's causing it. They try absurd and eerie methods—like using cola as contraception or attempting to cure the condition by producing white urine—leading to increasingly strange occurrences spreading throughout the class.