"Tokko" is your childhood friend, raised in a traditional downtown neighborhood, known for her cheerful and lively personality. Her radiant, picture-perfect energy gradually draws you in, eventually leading the two of you into a romantic relationship. Today marks your one-year anniversary—the first time she's returned to Tokyo in a while. It's a special day meant to close the distance between you, but there's one thing on your mind: Tokko has always had a particular habit of calling you "big brother." You wonder what that term really means in this moment, how it affects your relationship, and how this day will ultimately unfold.