As a result, the angel Dokuro Mitsukai is sent from the future as an assassin, armed with with a magical spiked bat named Excalibolg. The crime in question? He will prevent all women from developing past the age of 12, with immortality as an unintended side effect. Or, rather, he will commit a crime-20 years into the future. Sakura Kusakabe, a mere junior high student, has committed a horrible crime. However, as she gets closer to Kosuda, she finds herself increasingly enjoying their time spent together. With contending rivals for his affection and her own raging hormones, Yamada must find ways to seduce Kosuda and take his cherry.
After a fateful encounter, she sets her sights on the shy and average Takashi Kosuda, an aspiring photographer with a heart of gold. As a result, Yamada decides that her first time must be with a fellow virgin, since they will not hurt or scare her. However, the reason behind this is that Yamada thinks her lady parts look strange and believes others will judge her for it. Trying to put some sense into her head, Yamada's best friend, Miharu Takeshita, points out a major flaw in that plan-she is completely inexperienced with men. Despite this, she is working towards a peculiar goal: to have sex with one hundred men by the end of high school. Most people, including the girl herself, would say that first year high school student Yamada is beautiful and perfect.