There has long been a trend in anime of using random pop songs for openings rather than actually having specially made theme songs. Sometimes that works out just fine, other times not so much.
But one day a group of singers who didn’t like that trend got together and formed a group that would specialize in theme songs. And thus JAM Project was born.
Oh, did I mention that all those singers are very talented and that pretty much everything they’ve done as a group has been awesome?