This spring, I moved to Tokyo for work. I was raised to inherit my family's rural business and had planned to stay local, but an unexpected incident strongly drew me to Tokyo. I have a younger sister named Ichika. She always cared deeply for me, and we were known throughout the neighborhood as a close-knit brother and sister. However, as she grew older, her emotional dependence on me never faded—and one day, she suddenly confessed, "I'm in love with you, big brother..." Shocked by her words, I found myself emotionally stirred by her presence as a young woman, no longer the child I once knew, and ultimately gave in, committing an unforgivable act. Crushed by guilt, I decided to leave home in an attempt to distance myself from her. That decision became a turning point that drastically changed my life.