Seigaku's tennis team boards a luxury cruise ship for what promises to be a glamorous exhibition match. Soon after they arrive, a player on the opposing team introduces himself as Ryoma's older brother, and the claim leaves everyone stunned, Ryoma included. Then the truth emerges. The event's organizer is a wealthy millionaire running an illegal gambling scheme, and he makes it clear that the team will lose on purpose or face serious consequences. His fortune rides on the bets, and with armed staff aboard, he controls the rules here. Ryoma and his teammates face impossible choices: compete with integrity while trapped at sea with a man willing to exploit them, or give in. Tension builds across the ship as the players weigh their decisions, their bonds tested under pressure that reaches far beyond the court.