The story begins in a small, slightly unusual household, where the narrator, a young girl, has recently experienced a change in family dynamics. Her mother has re-married, bringing a new father and a brother into their lives. Though she still feels a little shy about calling them "お父さん" and "お兄ちゃん," she's happy about the new addition to the family. The new father is kind and close to her mother, but the brother is still a mystery — he doesn’t speak much to her, and she hopes they can become closer so she can naturally start calling him "お兄ちゃん."
Today marks the beginning of a trip for her parents, leaving the narrator alone with her new brother. The house feels different without her parents around — the usual comfort is replaced by a strange tension. As she prepares dinner, she tries to be brave, but the absence of her mother makes her feel a little nervous. The brother, though still quiet, seems to be paying more attention to her than usual, and that makes her even more aware of his presence.
As the night progresses, the quiet tension turns into something more intense. The brother's actions become more direct, and the narrator, though shy and a little scared, can’t help but feel the growing connection between them. Their interactions become more intimate, filled with moments of hesitation, fear, and eventual surrender. The brother's affection is both gentle and persistent, and the narrator finds herself caught between shyness and a growing sense of pleasure.
As the night comes to a close, the narrator finally relaxes, her body and emotions fully opened to the experience. She falls asleep with a soft smile, content in the warmth of the moment. In the quiet of the house, the bond between the brother and sister continues to grow, setting the stage for more moments to come.
