Tsuboi-kun no Switch!

The main character, Tsuboi Naoki, overdid it in soccer class one day and wore himself out. Afterward, he noticed a sign advertising for a massage service. He thought about paying with his pocket change and getting a masage for his weary body. Since he'd never paid for a massage before, somehow he felt a little more like an adult. When he went in, there was a beautiful older girl there working as a masseuse. She relaxed his body and restored him, but his strong desire for the girl caused him to unknowingly get an erection. From that moment he had truly climbed the steps to adulthood. With his longing still continuing fiercely and with his erection still unabated she made him cum many times more... From then on he thoroughly became a prisoner to the older girl's massages. He went to the parlor again, but he was worried about whether he could continue coming and sinking his pocket change into it. The girl smiled teasingly and offered a suggestion: "Maybe I could teach you how to massage and you could do it for your family and others? Getting a massage at home is pretty good, and it'd be a good advertisement, wouldn't it?　It would be nice if you did that and got us some new customers." He told the girl about his various desires and began giving massages to his stepmother and stepsister. As he did this, he gave no serious thought to what might become of it... [Translated from Fudegaki Soft's product page]