Panda and the Magic Serpent (1958) Anime Watch

As a young boy, Xu-Xian is forced to free his pet, a small snake. Unbeknownst to him, the snake is actually a young snake goddess named Bai-Niang and she is in love with him. Many years later, when they are both adults, the princess is magically transformed into a human and sets out to find her love. But the local wizard believes her to be a vampire, and banishes Xu-Xian from the village in order to save him. Xu-Xian's pet pandas Panda and Mimi set out to save him and bring him, in the process becoming leaders of an animal gang.