This is a story about how each of the popular girls in high school ends up having sex with the less popular guys. Ain't that wonderful and completely unrealistic? Maybe. But we're just here to fap so fuck logic.
It seems that everyone is fighting over Seiryu-kun's genes! They've even made a competition out of it! This is a crazy rom-com adventure, where a high school student and her friend are trying to get impregnated.