There can be many starting places. Which one you pick depends on where you're coming from, & in what direction you are going. It is probably wisest to select from those points where there is most co-incidence, since that way more journeys are possible.
Here there are two. One excludes itself, because that is where everything unravels; & though it also ties everything together there is no longer any anticipation, knowing the story, aware of what will happen next since it has already happened. The other, then, because that is where past & future coalesce, where a grain of pollen caught in the leg hairs of an ephemeral insect is brought in contact with another & fertilises it. Without the past there is nothing. Without the future there is no story.
So then the place to start is a ryokan famous for its onsen, its hot springs, at Lake Shikotsu, a caldera lake in Hokkaido. The year 1937, the month December. There is a conference going on disguised as a religious retreat, thirteen participants, twelve of whom are serving military officers with higher degrees, in history or cultural studies. The thirteenth, a civilian, acts as the de facto chairman. He holds several positions, Professor of Military History at Kyoto University, director of one of the largest zaibatsu (& linked by marriage to another), Cabinet Minister & a member of the currently secret Preparations for War oversight committee.
Six of the officers are Japanese. The others are two Germans & two Italians, a Spaniard & an American. They are paired, sharing rooms, one gaijin to each Japanese officer. The Professor has the best room in the inn to himself.