There has been an emperor in Japan for more than 15 centuries, making the Chrysanthemum Throne the world’s oldest monarchy. On Tuesday, Emperor Akihito stepped down, yielding to his eldest son in the first abdication in 200 years. In Episode 1 of this series, Akihito was the 12-year-old prince of a nation defeated in war. His story continues here.

Isao Chinen was biding his time, deep inside the island cave, waiting for the dignitary to arrive.

For six days, he and a fellow conspirator stayed out of sight, surviving on canned food, chocolate and biscuits. On the seventh, they huddled over a transistor radio to follow the news as the visitor approached.

Mr. Chinen was 25, a law student who had dropped out of university for this mission. Emerging from the cave that morning, in a khaki jumpsuit and a black helmet, he lit a Molotov cocktail, raised his arm high in the air and flung it at his target — Crown Prince Akihito.

“Down with the emperor!” he shouted. “Go home, C rown Prince !”