A kid trying to confess to his crush while literal aliens are invading is the entire joke, and the show never blinks about it. The G-On Riders are supposed to be Earth's defense line, but they're too busy fighting each other to notice the invasion is secondary to the real chaos happening inside the school. It's a show that knows the apocalypse is just background noise compared to the mess of actually being a teenager.

Saint Hoshikawa School harbors a secret: a covert group known as the G-On Riders. Students of superior strength and ability are selected to join it, and their task is to fight off aliens attacking the earth. Many of the troubles the members face come from within their own ranks, and the invaders have the same kind of trouble among themselves. Meanwhile Ichiro, another student at the school, keeps trying hard to confess his love to Yuki, one of the Riders. The show is a sci-fi comedy with dramatic and ecchi elements.