Hotaru, my girlfriend’s mischievous adult younger sister, is hopelessly into me. Eager to see my reaction, she keeps teasing me in thin tops with no bra, letting her nipples show through. “You’re always staring at my tits, aren’t you? I won’t tell my sister.” My lust keeps building as she flaunts her clothed breasts. When she notices my erection, she whispers, “Your cock is hard… You can do whatever you want to me.” Even though I already have a girlfriend, I finally give in to temptation and secretly fuck her sister.