While dating his girlfriend (played by Mahiro Yozora), a young man is introduced to her stunning older sister, Anri (played by Anri Okita). Despite the family connection, Anri begins to use her overwhelming physical charm and seductive nature to tempt him behind her sister's back. The story explores the tension and psychological struggle as he is drawn into a secret, physical relationship with the busty older sister, eventually crossing a line that puts his original relationship at risk.