the death of Mr. Mauller feels like of of the true earliest tragedies to hit Tenma this directly. Not that the death of his patient wouldn't have shook him. But this man helped him. Didn't have to. Did. This man BELIEVED him, when clearly no one else has. Took him seriously.
He wasn't a nice person. He wasn't an appealing person. He didn't shower often, he was fat, he was rude, he was a workaholic.
But he chose the side of good, and it cost him his life. He died to try and stop something terrible from happening.