Here's an idea. A group of Naruto characters visit a foreign land where boxing and hockey are popular. They meet a famous boxer who becomes their mentor in a way. They learn about the discipline and strategy in boxing and the teamwork in hockey. Meanwhile, an enemy from Naruto's world follows them and tries to disrupt their learning and newfound friendships. The Naruto characters then use what they've learned from boxing and hockey to fight this enemy and protect their new friends in this foreign land.
In a Naruto - inspired world, there could be a new sport that combines boxing and hockey. Naruto and his friends enter this sport. However, a powerful villain also has an interest in this sport. He tries to manipulate the rules and outcomes. The boxer - like skills of some characters, like Rock Lee, could be a great advantage in this new sport, and they have to fight against the villain's evil plans while also competing in this unique sport.
A boxer from our world could be reincarnated as a character in the Naruto universe. He discovers a form of hockey played on ice made of chakra. He decides to form a team with some Naruto characters and compete in a grand tournament. The team has to overcome rival teams who use underhanded ninja techniques during the games.