[Zork]

Thanks, that text dump helps a lot.

The events following dinner are much more chaotic so it's taking me quite some time to make sense of them. Just a couple points this time:

Spoiler:

Nanjo is upstairs in Kinzo's study. I'm less confident about this one because some pretty wild scenarios are theoretically possible. However, Battler & co. conduct a fairly exhaustive search and Nanjo was reported to have died inside the mansion. In the absence of any compelling reasons for lying about his death or moving his corpse, this would seem to be the answer.

Hideyoshi was shot in the head after the cousins left the mansion. The path they take to the guesthouse is described as a straight shot from the entrance through the rose garden, and Hideyoshi is found on a path that runs between the mansion and the rose garden after they loop back around to the main entrance. I really doubt they would simply miss him the first time.