One day Kuno bought a phoenix egg from an antiques salesman so he could learn the phoenix sword technique. Despite the shopkeeper's admonition not to place the egg on his head, Ranma unknowingly did so, causing the egg to hatch. The phoenix was revealed to be a hideous, pudgy bird with a phoenix-like tail. The first thing it saw was Ranma, imprinting on him as its enemy, which it would attack relentlessly. It could also generate a blinding flash of light as a defensive mechanism to keep attackers at bay.The only way to stop the phoenix was to using some growth pellets sold to him by the shopkeeper which would make the phoenix leave the nest (the top of Kuno's head) faster than the 100 years it would otherwise take.The phoenix ate the growth pellets, but grew so large that it nearly destroyed half the neighborhood. In the end, it finally left the top of Kuno's head only to leave another phoenix egg behind.
In the third movie, the phoenix was shown to imprint on a new enemy at the beginning of each day, imprinting on Akane when she went to deliver food to Ranma early in the morning, who was forced to camp overnight in an abandoned lot with Kuno and the phoenix in a tent. Although Ranma's initial attempts to feed the phoenix some growth pellets were defeated by Kuno, he was able to shove a bunch into its mouth in his girl form, making the phoenix grow and overshadowing Kuno's head. This made it easier to feed the phoenix because Kuno could not see, but the phoenix grew increasingly violent as it continued to grow, becoming so large that it could fly around at great speed and easily carry Kuno, while causing swathes of destruction with the downforce of the wind it generated while flying. Along with Akane and Ryoga's help, Ranma was able to keep feeding phoenix and Shampoo and Ukyo tried to attack it, but it generated a blinding flash of light that kept physical attacks at bay. At the end of the day, all the growth pellets had been used up, but in a blinding flash of light the phoenix left Kuno's head and flew away, leaving behind another egg.