The Seishun Academy Middle School tennis regulars are invited on a luxury cruise by Sakurafubuki Hikomaro to face his own team in a friendly match that quickly spirals into something far more dangerous and manipulation-filled than any practice session could be.
Aboard the ship, Ryoma Echizen Junko Minagawa discovers that Ryoga Echizen has introduced himself as Ryoma’s older brother, a revelation that unravels a long-hidden family history. Ryoma explains that Ryoga was adopted years earlier by Nanjiroh during their time in America, and that he vanished before Ryoma joined Seigaku. The tension between past loyalties and present ambitions begins to color every move on deck.
That evening, a banquet turns uneasy when Takashi Kawamura, the sushi chef, remarks that the food didn’t taste as expensive as it looked, hinting that appearances on the ship may be deceiving. In a quieter corner, Sadaharu Inui notices something off about the ship’s decor—he peels a patch of wallpaper and finds that the marble on the wall is fake, a small clue that this voyage is built on lies and schemes.
The following day, Sakurafubuki drops the brutal truth: the matches are part of an illegal gambling plot. If Seigaku purposely loses, Sakurafubuki stands to rake in money from bettors; if they win, their lives may be at stake. It becomes clear that everyone aboard—the passengers, the crew, and Sakurafubuki’s henchmen—could be using Seigaku as pawns in a dangerous game, leaving the team with little option but to rely on their own wits and teamwork.
As the pressure tightens, the team tries to devise a plan while still playing along with the rigged format, but the tension escalates when Kikumaru Eiji is caught eavesdropping, and the crew binds the group in a desperate escape attempt. Only Tezuka, Fuji, and Echizen are allowed to leave to compete in their assigned matches. Tezuka Ryotaro Okiayu and Fuji win their matches with calm authority, underscoring that resilience can still rise under duress.
Watching his younger rival in action, Ryoga contemplates breaking away from Sakurafubuki’s grasp and challenges the idea of being a mere pawn by proposing a direct match against his brother to test who has truly advanced as a player. Meanwhile, the rest of the team uses a combination of resourcefulness and timing to escape the room where they were held, aided by Inui’s clever use of his Juice and a string of humorous chases as the corrupt crew members give chase.
The escape is only temporary, and the group is recaptured and bound again by Sakurafubuki, who threatens them with a gun. Ryoma realizes that continuing the duel could put his teammates at grave risk, prompting Ryoga to take decisive action. He refuses to be Sakurafuki’s pawn any longer and fires a tennis ball straight into Sakurafuki’s forehead, breaking the hold over the ship and allowing the others to slip away once more.
The match between the Echizen brothers resumes as a violent storm rages. A massive tidal wave rolls over the cruise ship, forcing everyone to evacuate via lifeboats. Seigaku holds the line, guiding passengers to safety, though Momoshiro and Eiji tumble overboard during the chaos. The brothers keep playing underwater, unfazed by the wreckage and the flood of light that sweeps across the makeshift court. In a decisive moment, Ryoma’s return shot lands on Ryoga’s side of the net, even as the net has vanished and a great light blankets the arena, sealing Ryoma’s hard-won victory.
Ryoga accepts the loss with a quiet nod, and the two brothers reunite with their teammates as they manage to reach dry land and safety. Ryoga takes Ryoma’s hat, gives him an orange, and tells him to pursue his Grand Dream as the pair ride off toward the horizon on a jet ski.
The rescue arrives when Atobe Keigo appears by helicopter to oversee the evacuation and witness Sakurafuki’s arrest. In a prior phone exchange with Oshitari Yuushi and Gakuto Mukahi—who also appear on the scene—the two discuss how Seigaku’s invitation to the free cruise was part of Sakurafubuki’s scheme, and Atobe’s suspicions about the con prove correct as the ship sinks into a new chapter of their shared rivalry and camaraderie.
