My girlfriend's older sister is the famous celebrity Takasho, and we're all living together. One night, after drinking too much with the three of us, my girlfriend passed out, leaving just Takasho and me alone. When the conversation faded, she suddenly kissed me deeply, completely changing the atmosphere—and from that moment, there was no turning back. While my girlfriend was away on a trip, Takasho reached out, and for four fleeting days, I lived out a bittersweet lovers' fantasy with my girlfriend's older sister. This is the recorded chronicle of those four days, capturing the emotional shifts during our private moments together, the growing intimacy despite the guilt, and how our hearts drew closer even as we remained bound by unspoken boundaries.