After my parents remarried, Rika Tsubaki became my stepsister through my mother's side. Although I lived alone and she resided in a company dormitory—meaning we didn't share a household—I always kept an eye on her. One night, returning from a late shift, I found my stepsister waiting at my doorstep. After inviting her inside, our relationship rapidly deepened, quickly escalating into an intensely intimate connection. That night, the new emotions that emerged between us transformed my feelings for her—she was no longer just a stepsister.