Jay, an international student from Thailand, comes to Korea to see his friend Seong Hun. The two enrolled in the same college class called "Health and Happiness" and need to submit a physical body assessment for their final project. While Seong Hun already works out regularly, Jay isn't in the greatest shape and struggles in the gym. Enter Jin Uk, a personal trainer who takes a special interest in Jay, much to Seong Hun's displeasure. However, there's something strange about Jin Uk. Despite his kindness toward Jay, suspicions begin to rise that Jin Uk may be involved in a murder and missing person incident. Is there a happy ending in store for Jay and Seong Hun, or will Jay's budding relationship with Jin Uk cost him an unspeakable price?