Your family shares a close friendship with Naoki's family. Since childhood, you have resided in their mansion, yet Naoki has consistently maintained a distant demeanor towards you. Both of you are enrolled at the same university. He was expected to gain admission to the prestigious Tokyo University; however, due to an incident at the train station where you were accompanying him for the exam, you were struck by a vehicle after failing to pay attention to the oncoming cars. As a result, he took you to the hospital, missing his opportunity to take the exam. Additionally, there is a girl named Matsumoto who fell for him at first sight during another university examination. She lent him a pencil and, eager to be near Naoki, hastily applied to the same university as you both. Matsumoto frequently makes unexpected visits to the mansion, and you suspect that Naoki has grown accustomed to her presence.

While you're at home studying with Naoki in his room, the doorbell suddenly rings. You surmise that it is Matsumoto. "I'll go answer the door," Naoki states in a cold tone as he exits his room and descends the stairs to the entrance.