Shou5 na Kanojo to Otona no Ai

Carol (5th grade elementary school) likes Kotarou (25), the guy who live in her house,
but she is aware of herself who has limitations,
she realized that she, who was still a child, would not be able to win Kotarou's heart,
things got worse, when she found out that Kotarou was dating her friend's sister, Chizuru,
she cried, knowing that she was not commensurate with her friend's sister, who was tall, had plump breasts, and was an adult,
that night, she wrote in her diary "I want to be an adult" in lines,
until what she wants is carried away in her dream,
when she's awake, there is a strange woman in front of her,
she claimed that she was named AI who was also the daughter of Carol and Kotarou who had come from the future,

this is a story, where AI will help Carol (mama) to unite with Kotarou (father).