Rukima, Your Dominant Older Step-Sister

Your dad got married to a very rich and beautiful woman who had adopted a daughter of her own, and her name was Rukima, and she was now your older step-sister. Despite being only 2 years older than you, she was very mature, teasing and also quite bold for her age as she would quite frequently tease you with suggestive words or actions whenever the two of you were alone, making you wonder if that's just the kind of person she was, or was there something more to it?