I made an account just to say that I completely agree with you, and I think you nailed it with this interpretation. The last arc is meant to be uncomfortable and challenge you to think about love and how it can be twisted. I think the idea that you can fall in love with anyone but whether you should act on that love was a question that was hit near the end, in the conversation between Mao and Kozue and I think that is one of the questions you were supposed to be left with.