Kyo knew Kyoko — it’s something that is hinted at for many, many volumes, until it turns out to be an important part of both his and Tohru’s stories. Its earliest mention is in volume 4, where Kyo is cryptically shown to feel remorse at the sight of Kyoko’s grave. Their relationship isn’t fully shown until volume 16, where he narrates Kyoko’s backstory, and again in volume 20, where their interactions from a long time ago play out. This relationship is a crucial element of the series’ finale, as Kyo confesses to having known Kyoko in volume 21 in a confrontation with Tohru, and it takes the very last volume to clear the long-standing mystery behind their connection in its entirety. All of this makes Kyo the person shown to recall Kyoko the most often aside from Tohru.
As the Cat, Kyo isn’t acknowledged as part of the zodiac. Not only that, his “true form”, separate from his cat transformation, is considered a nauseating sight. As a result, Kyo has always been treated as a monster by the Sohma clan; even his own mother couldn’t bear his sight, showering him with false love until she took her own life because she couldn’t stand it anymore.
In his memories, Kyoko was the first person aside from his surrogate father who reached out to him instead of rejecting him, embodying the hope that as long as he’d continue to live, he’d eventually find someone who’ll accept him for who he is. The two first met close to her workplace when Kyo was still a child, back in the days when he would wander the streets after school so that he wouldn’t have to go home. Kyoko casually approached him to comment on his hair colour, but was met with irritation from Kyo’s side, something she considered endearing.
When she told him to go home quickly so as not to make his parents wait, he yelled that his mother was already dead, and that his father didn’t care whether or not he was dead or alive. Rather than dismissing those remarks and pretending to know better, Kyoko saw his loneliness for what it was.
I felt like crying. Back then, I didn’t even know what that word [loneliness] meant, but it was as if I had experienced forgiveness for my existence. By a complete stranger. Kyo, Volume 21
Though Kyo was cautious at their first meeting, he came back time and again to chat with her, and she’d tell him a lot about herself, her late husband Katsuya as well as Tohru. One day, Kyo found the usually energetic Kyoko in tears as she looked for her daughter who had gone missing. Seeing the one person who came closest to what would be considered a friend in such panic about a girl he had heard so much about, Kyo promised Kyoko that he’d find and bring back Tohru.
His search was fruitless, but after a while, Kyoko came to him to tell him Tohru had been found — by his long-standing rival Yuki of all people. Consumed by envy and feeling yet again outdone by the seemingly perfect Yuki, Kyo vented his frustrations to Kyoko, insisting on painting Yuki as a detestable person. Kyoko listened, as always, but this time, she said:
That’s how you want it to be, isn’t it? Because without a villain in your life, it’d be difficult for you, right? […] Talking about taking sides and who’s good and bad is silly. Is that kind of thing really worth worrying about? After all, you’re such a kind and good kid. Kyoko, Volume 20
What Kyoko meant to express was that Kyo ought to appreciate his own value as a person, rather than define himself by drawing comparisons to someone else. Unfortunately, that advice hit a sore spot, especially with Kyoko pointing out the truth behind Kyo needing someone to blame his own misery on while furthering it. Unable to take it, the young Kyo interpreted those words as Kyoko taking Yuki’s side. Feeling betrayed, he yelled “I don’t need someone like you!” at her and ran off.
Because he felt ashamed for not being able to save Tohru, and upset because Yuki had beaten him to it, he sulked and sulked instead of going back. Kyoko’s last words to him were “Don’t forget your promise!”, and it wouldn’t be until many years later that they’d meet again.
Kyoko, however, remained somewhere in his heart: a far-away memory of affection, of the promise of salvation, of a way out of the loneliness. And one day, he would meet the daughter she had spoken so fondly about in person, and come to cherish her so much more due to her connection with these memories of his.