Nagase can sound really good or he can overdo it and wind up screaming and horribly out of tune. I blame it on being overly enthusiastic, but it's a bit painful sometimes. And yeah, I think Jin and Tegoshi both have a tendency to go "Hey, look, I can sing!" and wind up blaring because they don't really know how to belt properly. (I'm hardly an expert on singing, but that's the impression I get.)