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It's interesting to read this manga up until now and reading the long comments from readers.
First, I do think that Nishigaki looks like Shirotani. But any event in our life could make one or two change/s inside us, like Kurose who is left by Nishigaki and feel guilty decides to help people like Nishigaki. That path leads him to Shirotani. It's possible that Kurose makes Shirotani as a substitute, but maybe not. Kurose wants to help Shirotani at first, clearly because the case reminds him of Nishigaki. But as times goes by, I think, yeah... Kurose might be really love Shirotani. It will be too complicated to explain things, so we need Nishigaki to show up alive in front of Kurose to clear the guilt inside of him and we know how his true feeling toward Shirotani.
Good luck for them! May happy ending be with you.
A moment before I read one of the really-helpful comment below, I almost write "Wait. What?!" because I don't understand the story.
So. Takumi and Yuzuru died. That's so sad. I prefer to not know about human-eating things. Really(/TДT)/