Xu Chun Mao, a gay man and sociologist, works as an assistant under the renowned Professor Li, both domestically and internationally. However, he struggles to deliver satisfactory results in his work. Prompted by Professor Li's casual remark, "Why don't you research the underworld?" Chun Mao ventures into society and among individuals vastly different from himself.

These individuals are crude, adorned with tattoos, heavy drinkers, and they recognize each other as brothers. Behind them lies the dark underbelly of society. Chun Mao becomes increasingly intrigued by what's happening and realizes he is more interested in the honest physical responses of these brothers at the bottom of the underworld.

Whether they are brothers enamored with shoes, immature minors, or those haunted by childhood traumas... Every debt among brothers must eventually be repaid, and Chun Mao, sinking deeper into this quagmire, is no exception.