Overview:

The protagonist is temporarily put in charge of the small massage parlor run by his parents.
It’s a quiet parlor with few customers.
By chance, the class representative from the protagonist’s class comes in for a massage that day.
She learns that her parents are out and heads off to get a massage, but…
Thinking that she might get to touch a girl’s body, the protagonist offers to give the massage herself, and an impromptu massage begins.