In author twitter there is an extra about them after the end (Sada is an angel btw). And also another extra about Sada's first love.
Okay, so, this is a very good ending. Mamiya, the cold scientist, ended up falling in love with someone. He wanted to be above everyone, for everyone to see him and his achievement. For him, this was the ultimate goal and a way to honour his aunt (although this was more of an excuse of his selfishness). He wanted to be in a world that would look up to him and him alone. After meeting Sada, everything changed. All his philosophy and ethics were in conflict. He wanted a world where there was just them. A world where they would get accepted. Now, nothing matters for him. It should be a movie.
Fuaa this story shows how delicate relationships are, whatever the kind. Delicate threads that can be broken anytime by anything: fading out because of time, place, life itself. Maybe thats fine
Maybe it is not.
This is the story of people who want to be together.
When people cannot put a name on something, they get scared, it is confusing, something that must be avoided. They have the NEED to label everything. Yeah, it is not wrong though, but, is it really something they have to do? Maybe.
The MCs are okay with their rs as it is now. They dont want to put any label on it. They are comfortable as it is. The people around them, well, they can't. Understandable, but like "why should they care what others say?" "If only they didn't care". Identity, orientation, relationships...most people need a label in order to not be confused, to feel they belong somewhere, that they are part of this society as "normal' as it can be.