Imaizumin-chi wa Douyara Gal no Tamariba ni Natteru Rashii

Imaizumi is a young regular highschooler, but somehow his house ended up as a hangout place for 3 girls from his school. The story starts off when the girls are playing a game in Imaizumi's room, while one of the girls is hugging him from behind as they play. The other girls get thirsty and decide to go to the grocery store to buy some snacks, leaving him and the blonde girl at the house. That's when the blondie takes action. After their arrival from the store, they see the boy and the girl doing it. The girls can't help but notice how exquisite his "thing" is and naturally they start playing a different kind of game.