Saki-chan has been taking Ma-kun (her boyfriend) for a month.
She gets a package one day, containing an "etiquette ball."
It said that "by placing this in your womb, it will clean out the smell and dirtiness."
However, once she put it inside her she couldn't get it out!
She sent an email to the company, that said they could easily take it out for her.
However, this was actually all a trap set up by an old man who saw her every morning.
He had sent her a test model of his "erotic ball" to deceive her.
She came into the company support center (secretly his lab) and...
The pure and loyal girl couldn't win against the power of the erotic ball (etiquette ball)
and ends up xxx with an old man she just met...