3.5, it was weird, but interesting. Man raises a demon child he found in the mountains. Let's it free at age 10. 7 years later they meet again and they do it. They separate, then meet again, but the demon "dies" defending the man from other demons. When he returns to the dead demon, his body was not there. YEARS later, when he's old and gray, dying, the man is carried back to the place the did it and had promised to meet each other again. Demon comes back, feeds him his flesh, and man becomes young and immortal with the demon.
Is this even yaoi?? It's tragedy tbh
Akatsubaki