When Takashi's dad remarries, he finds himself sharing a home with his new stepsister. Initially, he's worried about how awkward it might be to live with a girl, even if she is just his stepsister. But all those concerns fly out the window the moment he lays eyes on her. Her name is Alice, and she's a stunning beauty from Northern Europe. Takashi can't help but feel a mix of excitement and confusion, especially when he notices her rather generously sized chest.

Despite the stir of emotions, Takashi watches as Alice genuinely tries to fit into the family and make the best of their new situation. Determined to be a good older brother, he fights to keep his thoughts pure and treats her with respect. But one fateful day, everything changes when he accidentally catches a glimpse of her naked. The barriers he's carefully built up crumble in an instant, leaving him to deal with the flood of feelings he's been trying so hard to suppress.