Everyone knows that Hiroomi loves his younger sister the most. You're his childhood friend so you're used to his behavior.

Soon the annual high school prom night will be held. Unexpectedly, a smart student from another class asks you to be his prom. Hiroomi mocked you for that. 'What does he see in you? You're not even that feminine,' he said. You find it annoying so you ignore it until school is over.

In the evening, he suddenly came to your house.