Ryouma Echizen and the Seishun Academy Boys' Tennis Team are invited to participate in an exhibition game aboard a luxury cruise ship by its owner, Hikomaro Sakurafubuki. When they arrive, the boys are shocked to discover that Ryouma's adopted older brother, Ryouga, is the captain of the opposing team. During their first games, Seishun easily crushes their opponents, garnering excitement from the cruise spectators. However, many strange things about the cruise begin to surface—from the restaurant's cheap sushi to a bathroom covered in marble wallpaper. Suspecting something is amiss, the team quickly finds out that Sakurafubuki is running an illegal gambling plot and that they must lose their next set of matches in order for him to win a large sum of money. Back on the first day, their opponents were told to purposefully lose in order to make the spectators bet heavily on Seishun's victory. If the middle schoolers do not comply, they risk losing their lives, as all of the employees on the ship are armed and working with Sakurafubuki, including Ryouga. Relying only on themselves, the team must put their skills and intellect together to outsmart the threat around them. As Seishun decides to fight for their lives, the two sons of Samurai Nanjiro go head-to-head to determine who is the superior player. "Ryoma's brother?! Here comes Ryoga Echizen!"A conspiracy involving the members of the Aogaku tennis team takes place on a cruise ship. The ship sails along the Pacific, carrying a group of high profile celebrities from all over the world, enjoying their vacations. Among these flamboyant crowds are the members of the Aogaku tennis team, who have been cordially invited to play in the Exhibition Match on the cruise, hosted by a fanatic tennis-lover millionaire, Hikomaro Sakurafubuki.While the members are prepping for the match for the next day, a group of opponents walk up. Ryoma is cold and blunt as usual. But he is encountered by a boy who calls himself Ryoga Echizen, and says that he is Ryoma's elder brother. Everybody is flabbergasted, including Ryoma himself.That night, Tezuka and Oishi are called to Sakurafubuki's room and asked to lose the match tomorrow. The Exhibition Match turns out to be an illegal event, where the rich guests bet millions on the players. Threatened by Sakurafubuki to conspire in the gamble, the team hesitates having nowhere to get away to except for the ocean. Tezuka on the other hand refuses to give in, but what about the rest of the team? What about Ryoma?