The premise of the novel is reminiscent of the kind of extravagant metaphysical drama that Roger Zelazny was known for, and its psychedelic overtones reflect the zeitgeist of the time. Here's how the publisher's blurb describes it.
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.
Sounds trippy. This is one of the few works of Mitsuse-san's to be translated into English. Another is his novelette, The Sunset, 2217 A.D., which was included in Frederik Pohl's anthology, Best Science Fiction for 1972. Let's hope we see even more in the future.
10 Billion Days And 100 Billion Nights reviewed by Alan Cheuse