My younger sister masturbated every night on the lower bunk of the bunk bed, and finally couldn't hold back anymore... (Hasegawa Tsubaki, SERO-0080)

The younger sister idol 'Shizuka Hasegawa' has also appeared on EROTICA!! The older brother on the top bunk bed has been having sex with his girlfriend, and can only relieve his boredom by masturbating. Finally, one day, unable to suppress his desire any longer, the brother and sister cross the line of taboo...