This is a completely independent currency, developing separately from Bitcoin and its forks. The basis for the creation of Bytecoin was the unique CryptoNote technology.
It's the classic example of an interesting technology applied to a cryptocurrency, but the cryptocurrency ruins itself due a very bad distribution of the initial tokens. It's said that 80% of the tokens is in control of a tiny amount of people that mined it, mostly developers, they never made it public outside of the darknet or something along the lines. I would actually know the details on how this coin was launched and why it was replaced by Monero, because Monero is the fork that took over with the original Bytecoin technology.