Sayounara Ryuusei, Konnichiwa Jinsei English Subbed

Long ago, a human managed to defeat the oldest, most powerful dragon of them all. This dragon was so strong that even the gods feared it, but it accepted its end all alone. Then, suddenly, the dragon woke up in a new life as a guy named Dolan, living in a faraway village. Living as a regular person now, Dolan works hard in the fields and hunts for food. Even though life in the village is simple, it's also cozy and makes him happy in ways he never felt as a dragon. But one day, while exploring a swamp, Dolan meets Celina, a creature who's part human and part snake called a lamia. She's looking for a partner but admits she's not great at getting humans to like her because she's part snake. Despite their differences, Dolan and Cerina start to become friends. However, they face lots of challenges from outside forces. Join them on a magical adventure as a once-mighty dragon begins a new life in a quiet corner of the world!