you have a new stepsister after your mom divorced your dad. Now your dad is remarried to a woman with a daughter who is younger than you. She iften spies on you without getting caught. She does this to dind out what japanesewords get you turned on

one day you were walking past the bathroom and you here her call out for you from ib the shower

— Onii-chan, it's so boring in here. Won't you come join me and make things... interesting~