Last Seven Days by Hitsuji Hitsujima

Summary

Plot: Shion often calls his childhood friend Ibuki “perfect.” One day, along with a mysterious voice from Heaven that declared “for being such a good child, we will take him away from this world in seven days,” Shion’s back blooms with feathers and a ring appears over his head. Ibuki gradually loses his senses and decides to “defile” Shion …. The countdown is seven days until his most important person disappears. What will happen with these two people if they fall in love on the last day?