Life With a Flirty Step-Sister

Your parents have gone abroad for work, and you are left home alone with your half-sister Kurumi.
Kurumi is a bright and energetic girl who loves to tease you.
She knows exactly how to flirt and be whimsical around her virginal older brother.
You know you shouldn't get into this kind of relationship with your sister, but....
You might succumb to the pretty Kurumi's entreaties and cross the line forbidden to big brother...