妹のオモチャにされてしまう僕

When my mother remarried, I got a new step-sister. She's a cute girl in front of our parents. But when we're alone, her attitude changes... She insults me and steps on my crotch, she barges into my bath and makes me wash her, she makes me relieve stress, and she tells me to lick her sweaty feet. I can't resist my sister! Before I knew it, I was engrossed in our naughty acts, and I had become her toy.