Girl genius Yuni and heartthrob teacher Sakurai are in a secret relationship no one knows about. Yuni wants to celebrate her birthday with Sakurai, but he's so busy with work that she missed her chance and invited her friends to her house instead. Yuni's family also makes an appearance, and everyone is having a great time at the birthday party! But, as expected, she feels lonely without Sakurai there.... What will happen next?!