Kang Hee-jae desperately wants to appear cool to others, but secretly feels smaller than plankton on the inside. While struggling to forgive his girlfriend, Yoo-jin, for her “savage” behavior, he winds up gradually transforming into an obsessive monster.

Meanwhile, Ban Yoo-jin is a highly intelligent older student at Kang Hee-jae’s college. Because Yoo-jin can never seem to keep a relationship going for longer than 100 days, she starts to worry that she’ll wind up living a lonely life alone.

So when younger student Hee-jae boldly shoots his shot, she decides to put him through some intense “training” as they date.