Sayounara Ryuusei Konnichiwa Jinsei Episode 5

The strongest and oldest dragon who had lived through eternity allowed himself to be killed by Hero. Just as he prepared for eternal sleep, he realized himself reborn as Dran, a villager in the frontier. Working the field, hunting forest animal, and having a warm life has filled his heart with joy he never experienced in his whole dragon life. One day, when he's paroling the forest near his village, he encountered a powerful demon army...