A resurrection seems too fantastical a happy ending. It would have to be something closer to like Arashi figuring out how to touch Shiraishi and being together that way. I can already think of something like putting himself on the altar as an offering like with the clothes and then can astral project with shiraishi dragging him out or something. Despite my heart wanting love to prevail, I think what the story should do is tragic/bittersweet where shiraishi does pass on. We shouldn't cling to the dead, such is life.