With the robot anime a critical success, if not a financial one, the eizouken sets their sights on their next project. In order to maximize the potential gains for their grueling efforts, the time has come to produce something to sell at a local media convention. The stage is set for an alien invasion at Shibahama's self-published art expo, Comet A!
And the rumble is the excitation 
of an electric generator.
وصوت الدويّ هو صوت مولّدة كهربائية
E o ronco de um gerador elétrico...
А гул — это звук генератора.