Akatsubaki

"Is this feeling charity or inferiority?" A lonely young man, Sakichi, picked up a demon baby. He raised him and named him Aka, but in the future Aka returns to the mountains. However, Sakichi goes to the mountains in search of Aka because of a feeling in his heart even after time had passed. A non-human BL, depicting the frustration and deepening contact between humans and demons.

(Source: Futabasha, translated)