The male protagonist thinks that he has always been alone. His inferiority complex since childhood made him feel that he is not worthy of love and is not worthy of being liked by others.
The heroine shines very rarely in her life, so she is simply a cheerful and introverted little transparent who cannot be more transparent.
Plot idea: A high school student with low self-esteem meets a cheerful and introverted little transparent girl, but in the three years of junior high school, he has never liked her, and he doesn't know if he likes her. He feels that he doesn't deserve it, and he doesn't deserve her efforts.