Miki was secretly reading her younger brother's porn magazine when she became aroused and began masturbating. Suddenly, her brother's friend arrives and catches her in the embarrassing act. However, the situation only intensifies her arousal. As night deepens, Miki drinks alcohol to heighten her mood, while her brother returns home, drinks the leftover alcohol, and gets drunk. Amidst this, their relationship takes a deeper, more intimate turn.