I believe it has to do with an April Fool's joke on the Japanese server where Aris does a Let's Play Livestream video on the Game Development club newest game, Millennium Quest. However, the club made the mistake of making Yuuka as the Demon King, which pissed off Yuuka who was also watching the Livestream, which led to Yuuka rushing and kicking into the GDC's room and stopping the Livestream.