Sumire is a shy and modest otaku girl who loves erotic novels so much that she secretly masturbates in the classroom. One day, when she goes to deliver homework to her childhood friend Tatsuya, who is on the verge of failing, she is surprised to find a morning erection! Curious to see a man's genitalia for the first time, she can't resist inserting it raw into her pussy! Sumire becomes addicted to the pleasure of sex and the hard cock for the first time, and from that day on...