It says "After logging in on the official website, press Game Start".
It's useless atm. The game server and website shut down and we're awaiting for more info on the 21st(JP Time)
Translated News Courtesy to Laevatein http://closershq.com/Discussion-JP-Follo...suspension
Original Page https://cls.sega-online.jp/
If you want help or just want to chat ingame add IGN: Quan