Jitsushin Jun’ai Onsenkyou (RJ01306335)

After a long time, the protagonist “Makoto” and his sister “Asuka” decided to go on a hot spring trip together.

On the first day of the hot spring trip, Makoto finds Asuka’s freshly removed underwear. Unable to control his impulses, he gets excited and rubs his erect penis against his sister’s underwear. His lewd behavior is then discovered by his sister, Asuka.

This masturbation incident becomes the catalyst for a closer physical relationship between the siblings. Posing it as “training to get used to women,” Asuka seduces and milks Makoto repeatedly. As they go through this obscene training, the hidden feelings of both start to blossom…

And now, the siblings have crossed the line into a forbidden relationship…