Hi no Tori: Reimei-hen

In a mythical age of ancient Japan, Nagi Iza, a young boy living on one of the southern islands, is on a quest to find the legendary Phoenix and save his dying father. Believing the magical healing properties of the blood of the mysterious bird is the only way to cure his father, Nagi sets off on a mission to climb up Fire Mountain, a local volcano and the home of the Phoenix.

(Source: Tezuka in English)