Sunward Heart, Building a Tennis Empire: Long Kui's Anime Crossover Adventure

A thousand years after Long Kui, princess of the Jiang Kingdom, leapt into the sword-forging furnace, her soul did not fade into oblivion. Instead, a strange spatial disturbance carried her to a peculiar world filled with the sport of “tennis,” youthful energy, and, every now and then, shots that defied the laws of physics. She brought with her the pure ghostly power she had cultivated while sealed inside the Demon Sword, along with fragments of memories from her past life. This was the world of Prince of Tennis.