Well...damn. This was sad obviously, but also like...that ending is a bit confusing for me. I guess it's like a Ship of Theseus thing: if you replace a guy's entire body with someone else's, are they really the same person? But what confuses me is if the ending is the protagonist using the brother as a stand-in for Hisao, or if Hisao has become his brother. But maybe that's the point.