Ryo Shomonin was a genius who had graduated from Cambridge University's doctoral program. His specialty was quantum mechanics, often said to be the most difficult field in the natural sciences.
He had already secured a job offer at a research institute affiliated with his father's company and was aboard a plane with his wife for a pre-employment trip when suddenly he was enveloped in a blinding light, and his consciousness cut out.
Since it happened directly above the infamous Bermuda Triangle, it was impossible to tell whether it had been a plane crash or some occult phenomenon like an otherworldly transfer.
He died at the age of 27. He was married and had two young daughters.
His consciousness returned again when he was three years old. That was when he realized he retained memories from before his birth.
There was no way a three-year-old's intellect could make such judgments, so it had to be knowledge from his previous life.
In his previous life, there was the belief that souls undergo reincarnation, and indeed there were numerous reported cases of people born with fragments of past-life memories. The successive selection of the Dalai Lamas as reincarnations of their predecessors is a well-known example.
However, he retained his previous life's memories in almost complete form. He had never heard of such a thing.
If so, was this a dream? Yet it never ended, and his five senses felt completely real. In that case, it had to be interpreted as reincarnation.
His name after reincarnation was Friedrich Erde von Zähringen.
For a while after he became aware of things, he felt an unpleasant sense of having a dual personality, but after about three months, it settled down. There was no way a child could overpower an adult, so it felt as though the 27-year-old personality from his previous life had absorbed and integrated the three-year-old personality of his current life.
As he gradually grasped the situation of his present world, he realized that its geopolitical and cultural state closely resembled 13th-century medieval Europe from his previous life.
The country to which Friedrich belonged was called the "Holy Empire," but if events followed the course of his previous world's history, it would soon come to be known as the "Holy Roman Empire."
The town where Friedrich lived, Baden-Baden, as well as place names like the Black Forest (Schwarzwald) and neighboring countries such as the Kingdom of France were the same as in his previous life. The names of emperors and kings also matched historical figures from his former world.
At first, he suspected he had reincarnated into Earth's past, but there was one decisive difference that led him to reject that idea.
It was the appearance of the celestial bodies. Most noticeably, there were two moons. One was exactly the familiar moon from his previous life, but the other was small and dim. Unlike a perfect circle, it was distorted and shaped like a potato. As a result, the tides in this world moved in extremely complex patterns, making them very difficult to predict.
The constellations were also distorted compared to those he remembered from his previous life. The Milky Way appeared far brighter here.
Once he began listing the differences from his previous world, there was no end to them. In any case, it seemed certain that Friedrich had reincarnated not on Earth, but somewhere entirely different.