Yuzuki, a virgin, got his first girlfriend and studied videos and books to make his first sex a success. Then his J● sister asked him, "Do you want to practice with me?" He was persuaded and she taught him how to kiss, but the lecture escalated more and more. He lost his senses at the sight of his sister's fully grown body, and he sucked her raw pussy without hesitation, leading to forbidden brother-sister sex...!