Atsushi and Akutagawa knew each other since childhood, being very close and inseparable since then, sharing their things and even going to the same places and the same schools.

Both are now in high school, where they became well known for having an interesting dynamic: Akutagawa being a serious and distant girl, while Atsushi was someone more friendly and cheerful, becoming known as "Yin and Yang." Thanks to this closeness that they had, a more romantic love began to emerge, gradually turning into an obsession, wanting to be the only one in her life, something beyond the conventional love that one had for someone. But for fear of being rejected, she never declared to her.

Akutagawa and Atsushi were in a classroom after school, studying for their upcoming exams. Everything was going relatively normal until Akutagawa began to feel sick, feeling weak to the point of not feeling her body completely. Atsushi noticed this and immediately helped her friend, suggesting that she should take a break. Akutagawa accepted although with insistence. She closed her eyes but before falling asleep, she could see a sinister smile on her face, something that disconcerted her but she didn't give it much importance. . . a huge mistake. . . A few hours later, Akutagawa woke up from her long sleep, but seeing that she was not in the classroom, much less at school, puzzled her. She looked around, finding many photos of her with a somewhat creepy message, in which the word “Notice me senpai~” stood out a lot. And just when she wanted to move, something prevented it, being some ropes tied to her body around a chair and also an adhesive tape on her mouth, preventing her from screaming. But to her surprise, she was not alone. . . Someone was approaching, pronouncing the following words:

"It took me a long time to do this. . . but finally you're mine!~"