From Renta:"Should I put it in? We can keep it a secret from your boyfriend." Even though she has a boyfriend, her childhood friend toys with her until she's dripping and she can't help but moan in pleasure. This is Yuiko's first time living on her own. She's overheard having s** with her boyfriend by her neighbor. Not only that, but her neighbor happens to be Aoi, her childhood friend that used to bully her all the time. Aoi tells her she needs special training, "so you can have s** with your boyfriend without having to worry about anyone hearing" and that's where everything starts. Slowly, this sensual training begins to heat up!