Sochi, at the border between Krasnodarskiy Kray in Russia and Georgia.
Yarebin was born in Tbilisi, Georgia, but grew up in Sochi, so Sochi must have a significant and unique meaning in Yarebin's life.
Gao Yang knew that the Black Demons were cultivated from a young age. Of course, this 'young age' doesn't start at four or five years old; they generally begin to display the extraordinary talents required by the Black Demons around twelve or thirteen years old. Once noticed, they are selected and sent to the KGB, not exceeding the age of fifteen.
Once a person is over fifteen, their personality is mostly set; in other words, it's impossible to completely brainwash them.
The Black Demons are the epitome of learning throughout life because human life and energy are limited, while knowledge and skills are unlimited. To get as close as possible to omnipotence, they must learn and train.
