Based on the erotic game by Orcsoft. 
 
In school, there is a harsh reality that there are popular people, and those who live on the side lines. Those who are good at sports, look good, or have both, place higher on the hierarchy. There is an allure that you must have as a man or woman to place in this ranking. 
 
You are hanging out at a restaurant after going drinking with your classmates. Your childhood friend "Shiho" is sitting with you, and the both of you are those
who had lived on the side lines. The two most popular from the group had gotten together during the drinking party, and the two of you were wondering if they had gone to a love-hotel afterwords. 
 
"... maybe we can do it too. Sex." 
"what?" 
 
Knowing you are both virgins, you thought she was just acting tough. But she lowers her shirt to show you her meaty and healthy breasts, glistening with sweat. There was something undeniably lewd and arousing about those pale and soft mounds. 
 
"I know you've been staring at my breasts this whole time" 
"... well your face isn't great, but your body is super hot" 
"... you're the worst" 
 
She happily giggles this, and suddenly makes a proposal: 
 
"After we're done here, lets go to your place. No one else is home right?" 
 
(Source: DLsite English)

Sex Friend Osananajimi: Shojo to Doutei wa Hazukashii tte Minna ga Iu kara - The Animation