It began in 2019, with no institution behind it and no grant to answer to. Mitsui went to the places themselves: the stone circles and shell mounds of the Jomon in the far north, the moated villages where rice and bronze arrived with the Yayoi, the keyhole-shaped tombs of the Kofun age from Kyushu to the heart of Yamato.
He reads these sites beside the myths of the Kojiki and the Nihon Shoki and the shrines that still stand where those myths are set. He has followed the gods themselves, where each was worshipped and how they travelled, and the seafaring Ama peoples who carried them along the coasts and brought them ashore. Ancient history, archaeology, mythology, Shinto, Confucianism, folklore, spirituality and genetics: he crosses all of them and stays inside none.
And he has turned the inquiry on himself, reading his own whole genome to follow the lines that met in a single body. The question was never Japan's alone. Where did we come from, and what are we made of?