Sushigirl provides both IRC and Discord as chat options. Both services are linked together, so whichever you choose, you won't miss out on any conversation!
You can join the Discord server by Clicking This Invitation Link.
IRC is available for the client flavor of your choice at: irc.blackaster.xyz, port 6667 or port 6697 (SSL), channel #sushigirl. After presented with the welcome message, type /j #sushigirl to join the proper channel. NickServ is provided as well giving you a chance to register your name and prevent others from using it. Since the contents of #sushigirl are sent across the Discord bridge, they are part of the chat history in the Discord server, but other channels and messages on IRC are not logged or sent anywhere. You can create a private channel by joining it.
You can also visit the BlackAster IRC Web Client instead of using a software client.