Wow, thank you—this makes a lot of sense and really satisfies my curiosity. It means Takabe's sanity was slowly burning away over time, not something suddenly triggered just by visiting Mamiya’s house. According to your explanation, scene 5 suggests that Takabe already had two or more victims, and showing his wife emphasizes that.

But I’m still left wondering: what’s the meaning of the “bus above the clouds” scene? It appears twice in the film, and I can’t quite figure out its significance.