Responses
Did they both die in this manga?
Yes. Katou dies in his sleep because they both turned into idiots and didn't take him to the hospital. And Iwaki lives a good long life of loneliness and dies as an old man when his heart gives out.
What the hell that’s sad
I think the author is seriously a sadist by “killing” the lovers over and over even after the reincarnation from Fuyu no semi. Giving no chance to them to fulfill the promises they made to each other while they were both alive. Well, it was a great tragedy story in the end. ╥﹏╥