A year ago, Saeko remarried a man with a child and became the mother of a university student, Gaku. One day, "Mother, I decided to join the event circle." Saeko hoped that her university life would be fruitful while watching her smile and talk to Saeko. And a few days later, Manabu comes to the house with his circle friends. All the members who are doing some evil schemes for the summer event. Then, they come up with the idea of making Saeko drink the "original drink" they invented.