Tennis no Ouji-sama Movie 2: Eikokushiki Teikyuu Shiro Kessen!

Synopsis

Following the Nationals, Seishun Academy receives an invitation to participate in a junior tennis tournament at Wimbledon. In England, Ryouma Echizen and his teammates are joined by their rivals from Hyoutei Academy, Shitenhouji Middle School, and Rikkai University-Affiliated Middle School, who have also been invited to this special event. One evening before the start of the tournament, some of the players are attacked by a group of thugs, leaving them hospitalized with injuries. The only evidence distinguishing the assailants is a silver ring that each member wears on their hand and that their leader's name is Keith. In an effort to stop the gang, the middle school students convene to discuss their options but are interrupted by Ling Xiu, the person who saved Ryouma the night before. Xiu identifies himself as a former member of Clack—a band of tennis players banned from official competition due to their violent playstyles and conduct. The students are warned to stay out of the affairs of Clack as they cannot hope to win against their tennis style. Frustrated by the situation, Ryouma sneaks out with Xiu to confront Keith and the other members of Clack with the intent to take them down single-handedly. Knowing Xiu's true objective, Ryouma is now more determined than ever to defeat Keith to save the latter from himself. (Source: MyAnimeList)