In the world of the Republic of Korea, a unique coexistence exists between humans and beastmen, beings of contrasting nature. Tae-seong, a shark beastman, finds himself burdened with loan debt and in desperate need of winning a swimming competition’s prize money. However, his perennial rival, Yun-jae, always manages to claim the coveted first prize. One day, Tae-seong accidentally discovers Yun-jae’s human identity in the shower room. Seizing an opportunity, Tae-seong attempts to blackmail Yun-jae into repaying the debt, while promising to keep his secret concealed. Yet, despite his efforts, things don’t quite go as planned.