What's wrong with the title? It's not a tragedy right? ╥﹏╥

The title is the book's title one of the main character reads...but i can't say if the manga will be a tragedy

I think it means that the illusion of Hotaru will die, as in he will stop pretending to be Hotaru, or it will be discovered that he is pretending. Either way, I don't think it's very literal. Sometimes people say, "the you in my memories died that day" to describe a changing point in a relationship.