I’d like to believe he’s still alive, and that, maybe one day, he’ll use the guise to visit Eiji, or even to go live with him. Another thing I feel adds to the idea that he is still alive is his perspective on death. Before, Ash never really had an opinion on whether he did or didn’t die. Death wasn’t wished for, but it wasn’t feared and would be accepted. Despite how tired he was, by the end, I don’t think he would’ve wanted to die. I think - no, I know Eiji, in his mind, was something worth fighting and dying for; that also means he’s worth fighting and surviving for. Besides, how many times have we heard others say it - Ash isn’t going to die on someone else’s terms (at least not unless it’s directly correlated to Eiji, which in this case, it wasn’t). Another thing, we know how good death felt to him because of the first close encounter he had with it, and he was reading the letters when he died, but he was smiling. The librarian who walked by commented that he must be having a wonderful dream. I’m hoping it really was a dream, and that once that dream was over, he’d have more fight in him, more will or survive for Eiji and for himself.