I was given a chance by my stepsister to massage her

That night, I intended to borrow my stepsister's laptop to do my office duties, because my laptop was exposed to water. When I entered her room, she was lying down like she was exhausted. I offered to help massage her body, and my stepsister wanted to too. But the more I massaged her body, I realized that something was hardening under my pants, from the foot massage, I dared to move to her body part, when I lifted her shirt, I just realized that she wasn't wearing a bra at all, I gently rubbed her chest, then I opened her pants and I played with her with my fingers, she sighed in pleasure.