Você está descrevendo " O Monstro de Brighton " de Gerald Kersh. O viajante japonês do tempo foi nomeado Sato (um t) e o conceito de viagem no tempo através do bombardeio de Hiroshima e subsequentemente sendo descoberto pelos pescadores é definitivamente o cerne da trama.
O final do novela menciona ambos os aspectos;
Do you observe, by the way,' said the Colonel, pointing to the Reverend Titty's pamphlet, 'that poor little Sato was sick with running sores, and that his teeth were falling out? Radioactivity poisoning: these are the symptoms. Poor Sato! Can you wonder why he got desperate and simply chucked himself back into the sea to sink or swim? Put yourself in his position. You go to sleep in Hiroshima, in August 1945 and then—Whoof!—you find yourself in Brighton, in 1745.
No wonder the poor wretch couldn't speak. That shock would be enough to paralyse anyone's tongue. It scares me, Kersh, my boy—it puts a match to trains of thought of the most disturbing nature. It makes me remember that Past and Future are all one.