I still find it fucked that he'd compare his lovers to a fictional character (it'd be worse if it was a real person). Imagine how much it hurts finding out you were just a stand in for someone else, and that he's expecting you to act like her, like that would hurt so much. Cool that he stopped doing that though, and saw past the Hotaru in Niyama and loved him for who he actually was instead of who he ressembled so much of.
Hotaru wa Ashita Shinu