My choice was before the black plague in Europe, then wake up in the midst. Culture in the black plague was supposedly apocalyptic in nature, since so many were dying people thought the world was ending. You fall into a coma and wake up surrounded by people sick and dying, thinking the world was ending.
I wish I knew more about non-american (and by proxy European and roman) history. But I don’t.
Maybe someone who fell into a coma in 1952 during Stalin’s personality cult and woke up in 1957 when Khrushchev had tried to remove Stalin’s human rights abuses and cult of personality from the USSR.
I suspect he meant it was peaceful inside Japan itself. No warfare or bombings inside the borders and any hint of such in the near future would have been met with heavy disbelief. A Japanese waking up like that inside his country in late 1945 would have been in for quite a shock.