One day, Kouki Nakagawa was determined to declare his love to Ayumi Fujisaki, his childhood friend. Suddenly, a mysterious girl appears before them and mentions that she is Kouki's girlfriend, leaving both perplexed. After trying to talk to Ayumi again, Kouki confesses his love to her; But Jindou, the mysterious girl, warns Kouki that if he does not forget about Ayumi... the world will be destroyed! And her plan to have him give up on his feelings for Ayumi is... through lewd seduction?