Kyoko passed away in a car accident on her way to work during Tohru’s high school years — not too long before the beginning of Fruits Basket’s story. Her final moments are narrated from her own perspective in the very last volume, serving as a bridge between the aftermath of the lifted curse and the final act, which takes place after a brief timeskip.
In her last moments, Kyoko desperately clung to life, unable to accept that she was to die when Tohru still needed her, and wishing to accompany her daughter on her path much longer. Kyoko also thought back on what she had asked herself in a conversation with the young Kyo many years ago: whether it was more painful to be left behind or to leave others behind. Now, she had her answer: “Katsuya… I understand now that both leaving and being left behind are equally painful.”
Kyoko silently begged Tohru for her forgiveness, and prayed that someone would find and take care of the person most precious to her, and guide her when she’d be the lost. In that moment, her eyes caught sight of an older Kyo, and though his expression was that of pure shock, seeing him filled Kyoko with relief — they had made a promise after all.
Let Tohru find happiness. Let her be loved by many people. In spite of doubts and errors, let her be able to take pride in the life that she has lived in the end. Lead a life that you can look back on and say: “I persevered.” Because in life, good times follow bad times, and with each change, the years pile up. Kyoko, Volume 23
As a vision of heaven, the waves roll in and gently envelop Kyoko. When Katsuya approaches her, life returns to her eyes, and the young Kyoko in her school uniform takes Katsuya’s hand, reuniting with him at long last.
The very last page of the chapter shows the wide sea: the place where Kyoko first admitted to her feelings for Katsuya, and the site of their years of happiness.