A desire to touch a girl's body is a natural feeling for many men. But without a girlfriend, that desire remains unfulfilled. Unable to endure it any longer, I confided in my sister. To my surprise, she agreed—on the condition that it stay hidden under the sheets. "Only if it's under the covers... it's too embarrassing otherwise." Just her acceptance filled me with joy, but as she began kissing me and letting me touch her big tits, I lost control and forcefully entered her. Confused at first, she writhed beneath me, sweating heavily as her pleasure built. This moment marked the beginning of a new boundary in our relationship. Gradually, our moral boundaries crumbled, giving way to an entirely new connection.