Fushichou e no Tensei: Dragon Taoseru tte Futsuu no Tori ja Nai yo ne?

Somewhere in Japan a young boy spent much of his time in the hospital due to illness. Looking out from the hospital window, he always thought: "I want to be a bird a bird, and fly freely across the never ending sky." On that fateful day, he passed... Only to find himself reborn as a bird?! But he was different from a normal bird. they don't spit fire from their mouths, right? Now that he could finally fly, he set off, only to find the blue sky being blocked out by dark clouds. This is a story about an unusual bird who wants to fly freely under the blue sky, but is met with dark clouds, said to have adverse effects on all the creatures in the unknown kingdom of Nouzen.

(Source: Novel Updates)