Takahiro Matsui, a beautiful boy with a dazzling charm, enters Beiyu High School. There, his senior Yuji Tsukamoto, the president of a conglomerate, whom he admired in junior high school, also attends. Matsui joins the swim team and Tsukamoto confesses to him an incident that happened three years ago... (Source: J.C. Staff, translated)

Osakana wa Ami no Naka is a prequel to the manga of the same name.