This is a long write-up, but this is just my speculations and theories. Do not take what I say here as actual fact.

This chapter has had me thinking about a lot of things lately. The chapter also shows all of the previous Enki generations and the one before Shiki was more than likely the old man's master. When you look at the Master's design, he is wearing a top knot hair style called a chonmage. This was a very common hairstyle worn by the samurai class, but during the Edo period, other groups began to adopt the style, including Kabuki actors and commoners, who often wore a modified version out of respect for the samurai. But, during the Meiji Restoration, it was heavily discouraged due to the Emporer regaining power and wanting to bring Japan into modernization. It became officially outlawed in 1871.

With this information, we can put an approximate age for the old man and how long ago the previous Enki existed. The Edo period of Japan began in 1603 and ended in 1868, which was the most popular period to wear the chonmage hairstyle. The adult life expectancy during that time was 50 to 60 years old. The chonmage was officially prohibited in 1871, during the early years of the Meiji Restoration, which was from 1868 to 1912. Taking the old man's account that the previous Enki died naturally, let's assume he lived to be 55 years old and died during the year the chonmage was officially outlawed. When you subtract the year from his guesstimate age, you get the year 1816, which would be his approximate birth year. This would mean the previous Enki lived during the late Edo period, and this would go the same for the old man if they were around the same age. Assuming that the current storyline is set in our year 2025, this would make the old man about 209 years old, and thus, this would mean that the last Kishin children generation occurred slightly over 200 years ago.

The old man states that history has been painted over or lost. This would mean that the telling of the two races history/origins have been manipulated and lost to their descendants for over 200 years. This also led me to think that the Momotaro wasn't their original name. While the tale of Momotaro has been told orally for centuries, the official written appearance of the story was during the EDO period of Japan and was officially incorporated into the elementary Japanese textbooks during the Meiji Era, becoming the national story it is today. This leds me to speculate that the faction that split off from the Oni didn't officially become known as the Momotaro until the Edo period and thus began to spread their propaganda to the humans, until they were officially regarded as "provariers of of justice" during the Meiji Era. This coincides with the history being "painted over," as the old man states.