Takanashi Nao's massive crush on her adoptive older brother Shuusuke grows. But her best friend Iroha will not be overshadowed, as she desperately competes for Shuusuke's affection in an ever-escalating battle. Meanwhile, class president Mayuka has introduced a secret weapon that Shuusuke can't possibly resist. As Nao and Iroha strive to outdo Mayuka, frisky Shuusuke struggles to keep his cool - and more importantly, his sanity.