>>1577>>1578>>1579I agree with your idea of what their relationship might have been like. In my mind, Masada was her kind, caring piano teacher that gave her a place she could feel safe at. With someone she knew she could trust.
I also believe Masada understands her on personal levels and they came together as two people badly hurt to lean on each other.
As for Mars-san, I believe he, plus the broken down train, represents something happening to Masada. Likely he was killed. The ship crashing symbolizing their world crumbling to disaster/sorrow.
That's my opinion anyway.