Monacoin trading is not available on Bitflyer. It's also not mentioned at all in the press release (while Litecoin trading, etc, are stated to launch in the first half of 2018). Whether or not this means Bitflyer USA will trade Monacoin or not is still up in the air, but I can at least confirm that as of launch (and today) that only USD-BTC trading is active on Bitflyer.