I don't read Japanese, but with the help of my friend the internet I can sometimes construe a bit of it. But, man, what a language. There are three different writing systems at work in this panel. I think what's being said is, "Oh, that Katamari. Choir club?" Katamari is a video game publisher, so I imagine this character is reacting to the news that the school choir is going to rehearse a song from some video game. If this were Genshiken Kio Shimoku would have used a parody name for the company, but as the practice of Hashikko Ensemble is to reference real songs the reader will know he uses the company's actual name.
Figuring out Japanese texts is a rewarding mental exercise, but I will be very much obliged to the publisher who brings Hashikko Ensemble out in English.