Ashura (or Ashura-Ou) with Shurato from the manga RG Veda (by Clamp also known as “HairPorn”).
It’s an old manga you probably don’t remember or didn’t read. To be honest, I think it’s the only one I really loved from Clamp. Not that I didn’t like the others, but well, didn’t love them either.
Spent a lot of time on this one, but it was worth it, I had fun.