Plato, Buddha, Christ--what brings these men to the far future to witness the end of the world?

Ten billion days—that is how long it will take the philosopher Plato to determine the true systems of the world. One hundred billion nights—that is how far into the future Jesus of Nazareth, Siddhartha, and the demigod Asura will travel to witness the end of all worlds. Named the greatest Japanese science fiction novel of all time, Ten Billion Days and One Hundred Billion Nights is an epic eons in the making. Originally published in 1967, the novel was revised by the author in later years and republished in 1973.